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Abstract:

Provided are a heterocyclic compound which emits blue light and is
represented by General Formula (G1) below, and a light-emitting element,
a light-emitting device, an electronic device and a lighting device which
are formed using the heterocyclic compound represented by General Formula
(G1) below. The use of the heterocyclic compound represented by General
Formula (G1) makes it possible to provide a light-emitting element which
has high emission efficiency, and also a light-emitting device, an
electronic device and a lighting device which have reduced power
consumption.
##STR00001##

Claims:

1. (canceled)

2. A compound represented by General Formula (B1), ##STR00101## wherein
R8 to R18 independently represent a hydrogen atom, an alkyl
group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl
group having 6 to 13 carbon atoms, wherein R101 and R102
independently represent a hydrogen atom or an alkyl group having 1 to 6
carbon atoms, and wherein X represents oxygen or sulfur.

3. The compound according to claim 2, wherein R101 and R102 are
the same.

4. The compound according to claim 2, wherein R101 and R102 are
different from each other.

5. The compound according to claim 2, wherein R101 and R102 are
combined with each other to from a ring.

6. A compound represented by General Formula (B2), ##STR00102## wherein
R8 to R18 independently represent a hydrogen atom, an alkyl
group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl
group having 6 to 13 carbon atoms, wherein R101 and R102
independently represent a hydrogen atom or an alkyl group having 1 to 6
carbon atoms, and wherein X represents oxygen or sulfur.

7. The compound according to claim 6, wherein R101 and R102 are
the same.

8. The compound according to claim 6, wherein R101 and R102 are
different from each other.

9. The compound according to claim 6, wherein R101 and R102 are
combined with each other to from a ring.

10. A compound represented by the following structural Formula:
##STR00103##

11. A compound represented by the following structural Formula:
##STR00104##

12. A compound represented by the following structural Formula:
##STR00105##

Description:

[0001] This application is a continuation of copending U.S. application
Ser. No. 14/301,957, filed on Jun. 11, 2014 which is a continuation of
U.S. application Ser. No. 12/942,214, filed on Nov. 9, 2010 (now U.S.
Pat. No. 8,771,840 issued Jul. 8, 2014), which are all incorporated
herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a heterocyclic compound. Also, the
present invention relates to a light-emitting element, a light-emitting
device, an electronic device, and a lighting device using the
heterocyclic compound.

[0004] 2. Description of the Related Art

[0005] In recent years, research and development have been extensively
conducted on light-emitting elements using electroluminescence (EL). In
the basic structure of such a light-emitting element, a layer which
contains a light-emitting substance is interposed between a pair of
electrodes. By voltage application to this element, light emission from
the light-emitting substance can be obtained.

[0006] Since such light-emitting elements are self-luminous elements, they
have advantages over liquid crystal displays in having high pixel
visibility and eliminating the need for a backlight, for example, thereby
being considered as suitable for flat panel display elements.
Light-emitting elements are also highly advantageous in that they can be
thin and lightweight. Furthermore, very high speed response is one of the
features of such elements.

[0007] Furthermore, since such light-emitting elements can be formed in a
film form, they make it easy to provide planar light emission, thereby
achieving large-area elements utilizing planar light emission. This is
difficult to obtain with point light sources typified by incandescent
lamps and LEDs or linear light sources typified by fluorescent lamps.
Thus, light-emitting elements have great potential as surface light
sources applicable to lightings and the like.

[0008] A light-emitting element utilizing EL is driven by injection of
electrons from a cathode and holes from an anode into a layer containing
a light-emitting substance which is interposed between a pair of
electrodes. The electrons injected from the cathode and the holes
injected from the anode recombine in the layer containing the
light-emitting substance to form molecular excitons. The molecular
excitons release energy in returning to a ground state. In the case where
the energy is released as light having a wavelength corresponding to that
of visible light, light emission can be seen. Excited states of organic
compounds can be a singlet state and a triplet state, and light emission
can occur either of the excited state.

[0009] The emission wavelength of a light-emitting element is determined
by the difference of energy between the ground state and the excited
state, that is, an energy gap. Therefore, by appropriate selection or
modification of a structure of the molecule that contributes to light
emission, any color of light can be obtained. When a light-emitting
device is fabricated using light-emitting elements capable of emitting
light of red, blue, and green, which are the three primary colors of
light, the light-emitting device can perform full color display.

[0010] Manufacture of high performance full-color light-emitting devices
needs red, blue, and green light-emitting elements which are excellent in
lifetime, emission efficiency, and the like. The recent development of
materials has achieved good characteristics of red and green
light-emitting elements. However, as for blue light-emitting elements,
sufficient characteristics have not been obtained. For example, Patent
Documents 1 and 2 reported a light-emitting element having relatively
high emission efficiency. However, in order to realize high performance
full-color displays, further higher emission efficiency have been
required.

[0013] An object of one embodiment of the present invention is to provide
a novel heterocyclic compound that exhibits blue light emission. Another
object of one embodiment of the present invention is to provide a
light-emitting element having high emission efficiency. Still another
object of an embodiment of the present invention is to provide a
light-emitting device, an electronic device, and a lighting device in
each of which power consumption is reduced by use of the above
light-emitting element.

[0014] An embodiment of the present invention is a heterocyclic compound
having a structure represented by General Formula (G1) below.

##STR00002##

[0015] In General Formula (G1), Ar1 and Ar2 independently
represent a substituted or unsubstituted aryl group having 6 to 13 carbon
atoms, R1 to R11 independently represent any of hydrogen, an
alkyl group having 1 to 4 carbon atoms, and a substituted or
unsubstituted aryl group having 6 to 13 carbon atoms, and A represents a
substituent represented by General Formula (S1) or (S2). In General
Formulae (S1) and (S2), X represents oxygen or sulfur, and R12 to
R18 independently represent any of hydrogen, an alkyl group having 1
to 4 carbon atoms, and a substituted or unsubstituted aryl group having 6
to 13 carbon atoms.

[0016] Another embodiment of the present invention is a heterocyclic
compound having a structure represented by General Formula (G2-1) below.

##STR00003##

[0017] In General Formula (G2-1), Ar1 and Ar2 independently
represent a substituted or unsubstituted aryl group having 6 to 13 carbon
atoms, X represents oxygen or sulfur, and R1 to R18
independently represent any of hydrogen, an alkyl group having 1 to 4
carbon atoms, and a substituted or unsubstituted aryl group having 6 to
13 carbon atoms.

[0018] Yet another embodiment of the present invention is a heterocyclic
compound having a structure represented by General Formula (G3) below.

##STR00004##

[0019] In General Formula (G3), Ar1 and Ar2 independently
represent a substituted or unsubstituted aryl group having 6 to 13 carbon
atoms, X represents oxygen or sulfur, and R1 to R7 and R12
to R18 independently represent any of hydrogen, an alkyl group
having 1 to 4 carbon atoms, and a substituted or unsubstituted aryl group
having 6 to 13 carbon atoms.

[0020] Another embodiment of the present invention is a heterocyclic
compound having a structure represented by General Formula (G4) below.

##STR00005##

[0021] In General Formula (G4), Ar1 and Ar2 independently
represent a substituted or unsubstituted aryl group having 6 to 13 carbon
atoms, and X represents oxygen or sulfur.

[0022] As the heterocyclic compound of one embodiment of the present
invention, there are a dibenzofuran derivative and a dibenzothiophene
derivative each having the structure represented by the above General
Formula (G1). Therefore, another embodiment of the present invention is a
dibenzofuran derivative having a structure represented by Structural
Formula (100) below.

##STR00006##

[0023] Still another embodiment of the present invention is a
dibenzothiophene derivative having a structure represented by Structural
Formula (300) below.

##STR00007##

[0024] The above heterocyclic compounds which are embodiments of the
present invention represented by any of General Formulae (G1), (G2-1),
(G3), and (G4) and Structural Formulae (100) and (300) can be preferably
used as a material for a light-emitting element or an organic device such
as an organic transistor. Therefore, a light-emitting element including
the above heterocyclic compound is one embodiment of the present
invention.

[0025] Another embodiment of the present invention is a light-emitting
element including a light-emitting layer that includes the above
heterocyclic compound. The heterocyclic compound which is one embodiment
of the present invention exhibits blue light emission and high emission
efficiency, and therefore can be preferably used as a material for a
light-emitting layer of a light-emitting element.

[0026] Still another embodiment of the present invention is a
light-emitting element including a light-emitting layer that includes the
above heterocyclic compound and a light-emitting substance. The
heterocyclic compound which is one embodiment of the present invention
has a wide energy gap. Therefore, in a light-emitting element, such a
heterocyclic compound achieves high emission efficiency, when used as a
host material in which the light-emitting substance of the light-emitting
layer is dispersed. In particular, when the heterocyclic compound is used
as a host material for a blue light-emitting substance, a blue
light-emitting element having high emission efficiency can be provided.

[0027] Yet another embodiment of the present invention is a light-emitting
element having at least a light-emitting layer and a hole-transport layer
between a pair of electrodes, in which the hole-transport layer includes
the above heterocyclic compound. Since the heterocyclic compound of one
embodiment of the present invention has a high hole-transport property,
the heterocyclic compound can be preferably used as a material for the
hole-transport layer.

[0028] Since the light-emitting element of one embodiment of the present
invention which is obtained as above can realize high emission
efficiency, a light-emitting device (such as an image display device)
using this light-emitting element can realize low power consumption.
Therefore, a light-emitting device using the above light-emitting element
is one embodiment of the present invention. In addition, an electronic
device and a lighting device using the light-emitting device are also
embodiments of the present invention.

[0029] The light-emitting device in this specification cover an image
display device using a light-emitting element and also the following
devices: a module including a light-emitting element to which a connector
such as an anisotropic conductive film, a tape automated bonding (TAB)
tape, or a tape carrier package (TCP) is added; a module in which the top
of the TAB tape or the TCP is provided with a printed wiring board; a
module in which an integrated circuit (IC) is directly mounted on a
light-emitting element by a chip on glass (COG) technique; and the like.
Furthermore, a light-emitting device used in a lighting device and the
like is also included.

[0030] One embodiment of the present invention can provide a novel
heterocyclic compound that exhibits blue light emission. Further, the
heterocyclic compound which is one embodiment of the present invention
has high emission efficiency. Therefore, by using the heterocyclic
compound of one embodiment of the present invention for a light-emitting
element, the light-emitting element can have high emission efficiency.
Further, the use of the heterocyclic compound of one embodiment of the
present invention enables the production of a light-emitting device, an
electronic device, and a lighting device in each of which power
consumption is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIGS. 1A and 1B each illustrate a light-emitting element of one
embodiment of the present invention.

[0032] FIGS. 2A and 2B each illustrate a light-emitting element of one
embodiment of the present invention.

[0033] FIGS. 3A and 3B illustrate a light-emitting device of one
embodiment of the present invention.

[0034] FIGS. 4A and 4B illustrate a light-emitting device of one
embodiment of the present invention.

[0035] FIGS. 5A to 5D each illustrate an electronic device of one
embodiment of the present invention.

[0036] FIG. 6 illustrates a lighting device according to one embodiment of
one embodiment of the present invention.

[0037] FIG. 7 illustrates a lighting device according to one embodiment of
the present invention.

[0038] FIG. 8 illustrates a lighting device according to one embodiment of
the present invention.

[0085] Embodiments of the present invention will now be described with
reference to the accompanying drawings. Note that the invention is not
limited to the description below, and it will be easily understood by
those skilled in the art that various changes and modifications can be
made without departing from the spirit and scope of the invention.
Therefore, the invention should not be construed as being limited to the
description in the following embodiments.

Embodiment 1

[0086] In Embodiment 1, a heterocyclic compound of one embodiment of the
present invention is described.

[0087] One embodiment of the present invention is the heterocyclic
compound represented by General Formula (G1).

##STR00008##

[0088] In General Formula (G1), Ar1 and Ar2 independently
represent a substituted or unsubstituted aryl group having 6 to 13 carbon
atoms, R1 to R11 independently represent any of hydrogen, an
alkyl group having 1 to 4 carbon atoms, and a substituted or
unsubstituted aryl group having 6 to 13 carbon atoms, and A represents a
substituent represented by General Formula (S1) or (S2). In General
Formulae (S1) and (S2), X represents oxygen or sulfur, and R12 to
R18 independently represent any of hydrogen, an alkyl group having 1
to 4 carbon atoms, and a substituted or unsubstituted aryl group having 6
to 13 carbon atoms. Note that the carbon atoms in an aryl group in this
specification mean carbon atoms which form a ring of the main skeleton,
not including carbon atoms in a substituent bonded to the main skeleton.

[0089] Another embodiment of the present invention is a heterocyclic
compound (G2-1) in which, in General Formula (G1), A is the substituent
represented by General Formula (S1).

##STR00009##

[0090] Because of its easy synthesis, preferred is a heterocyclic compound
(G3) of one embodiment of the present invention in which, in General
Formula (G2-1), R8 to R11 are each substituted with hydrogen.

##STR00010##

[0091] Because of its easy synthesis, further preferred is a heterocyclic
compound (G4) of one embodiment of the present invention in which, in
General Formula (G2-1), R1 to R18 are each substituted with
hydrogen.

##STR00011##

[0092] Still another embodiment of the present invention is a heterocyclic
compound (G2-2) in which, in General Formula (G1), A is the substituent
represented by General Formula (S2).

##STR00012##

[0093] As specific structures of Ar1 and Ar2 in General Formula
(G1), there are substituents represented by Structural Formulae (1-1) to
(1-16).

##STR00013## ##STR00014## ##STR00015##

[0094] As specific structures of R1 to R11 in General Formula
(G1), there are substituents represented by Structural Formulae (2-1) to
(2-9) in addition to Structural Formulae (1-1) to (1-16) above.

##STR00016##

[0095] As specific structures of R12 to R18 in General Formulae
(S1) and (S2), there are substituents represented by the above-described
Structural Formulae (1-1) to (1-16) and (2-1) to (2-9).

[0096] Specific examples of the heterocyclic compound represented by
General Formula (G1) include, but not limited to, dibenzofuran
derivatives represented by Structural Formulae (100) to (203) and
dibenzothiophene derivatives represented by Structural Formulae (300) to
(400).

[0097] A variety of reactions can be applied to a synthesis method of the
heterocyclic compound which is one embodiment of the present invention.
For example, synthesis reactions described below enable the synthesis of
the heterocyclic compound of one embodiment of the present invention
represented by General Formula (G1). Synthesis Method 1 is a method of
synthesizing the heterocyclic compound (G2-1) of one embodiment of the
present invention in which, in General Formula (G1), A is the substituent
represented by General Formula (S1). Further, Synthesis Method 2 is a
method of synthesizing the heterocyclic compound (G2-2) of one embodiment
of the present invention in which, in General Formula (G1), A is the
substituent represented by General Formula (S2). Note that the synthesis
methods of the heterocyclic compound which is one embodiment of the
present invention are not limited to the synthesis methods below.

[0099] The heterocyclic compound (G2-1) of one embodiment of the present
invention can be synthesized according to Synthesis Scheme (A-1).
Specifically, a halogen compound of an anthracene derivative (Compound A)
is coupled with an organoboron compound of a dibenzofuran derivative or a
dibenzothiophene derivative (Compound B1) according to a Suzuki-Miyaura
reaction using a palladium catalyst, whereby the heterocyclic compound
(Compound G2-1) described in this embodiment can be provided.

[0100] In Synthesis Scheme (A-1), X represents oxygen or sulfur. In
Synthesis Scheme (A-1), D represents a halogen. As the halogen, iodine or
bromine is preferable.

[0101] In Synthesis Scheme (A-1), R101 and R102 independently
represent hydrogen or an alkyl group having 1 to 6 carbon atoms, may be
the same or different from each other, and may be combined with each
other to form a ring.

[0102] Examples of the palladium catalyst that can be used in Synthesis
Scheme (A-1) include palladium(II) acetate,
tetrakis(triphenylphosphine)palladium(0), and the like. Examples of a
ligand of the palladium catalyst which can be used in Synthesis Scheme
(A-1) include tri(ortho-tolyl)phosphine, triphenylphosphine,
tricyclohexylphosphine, and the like.

[0103] Examples of a base that can be used in Synthesis Scheme (A-1)
include an organic base such as sodium tert-butoxide, an inorganic base
such as potassium carbonate, and the like.

[0104] Examples of solvents that can be used in Synthesis Scheme (A-1)
include a mixed solvent of toluene and water; a mixed solvent of toluene,
alcohol such as ethanol, and water; a mixed solvent of xylene and water;
a mixed solvent of xylene, alcohol such as ethanol, and water; a mixed
solvent of benzene and water; a mixed solvent of benzene, alcohol such as
ethanol, and water; a mixed solvent of an ether such as
1,2-dimethoxyethane and water; and the like. Use of a mixed solvent of
toluene and water or a mixed solvent of toluene, ethanol, and water is
more preferable.

[0105] Thus, the heterocyclic compound of this embodiment can be
synthesized.

[0107] The heterocyclic compound (G2-2) of one embodiment of the present
invention can be synthesized according to Synthesis Scheme (B-1).
Specifically, a halogen compound of an anthracene derivative (Compound A)
is coupled with an organoboron compound of a dibenzofuran derivative or a
dibenzothiophene derivative (Compound B2) according to a Suzuki-Miyaura
reaction using a palladium catalyst, whereby the heterocyclic compound
(Compound G2-2) described in this embodiment can be provided.

[0108] In Synthesis Scheme (B-1), X represents oxygen or sulfur. In
Synthesis Scheme (B-1), D represents a halogen. As the halogen, iodine or
bromine is preferable.

[0109] In Synthesis Scheme (B-1), R101 and R102 independently
represent hydrogen or an alkyl group having 1 to 6 carbon atoms, may be
the same or different from each other, and may be combined with each
other to form a ring.

[0110] Examples of the palladium catalyst that can be used in Synthesis
Scheme (B-1) include palladium(II) acetate,
tetrakis(triphenylphosphine)palladium(0), and the like. Examples of a
ligand of the palladium catalyst which can be used in Synthesis Scheme
(B-1) include tri(ortho-tolyl)phosphine, triphenylphosphine,
tricyclohexyiphosphine, and the like.

[0111] Examples of a base that can be used in Synthesis Scheme (B-1)
include an organic base such as sodium tert-butoxide, an inorganic base
such as potassium carbonate, and the like.

[0112] Examples of solvents that can be used in Synthesis Scheme (B-1)
include a mixed solvent of toluene and water; a mixed solvent of toluene,
alcohol such as ethanol, and water; a mixed solvent of xylene and water;
a mixed solvent of xylene, alcohol such as ethanol, and water; a mixed
solvent of benzene and water; a mixed solvent of benzene, alcohol such as
ethanol, and water; a mixed solvent having an ether such as
1,2-dimethoxyethane and water; and the like. Use of a mixed solvent of
toluene and water or a mixed solvent of toluene, ethanol, and water is
more preferable.

[0113] Thus, the heterocyclic compound of this embodiment can be
synthesized.

[0114] The heterocyclic compound of this embodiment emits blue light and
has a hole-transport property. Also, the heterocyclic compound of this
embodiment exhibits high emission efficiency. Accordingly, with the use
of the heterocyclic compound of this embodiment for a light-emitting
element, the light-emitting element can exhibit high emission efficiency.
Further, the use of the heterocyclic compound of this embodiment can
provide a light-emitting device, an electronic device, and a lighting
device each having reduced power consumption.

Embodiment 2

[0115] In Embodiment 2, a light-emitting element in which the heterocyclic
compound of one embodiment of the present invention is used for an EL
layer will be described with reference to FIGS. 1A and 1B.

[0116] In the light-emitting element of this embodiment, the EL layer
having at least a light-emitting layer is interposed between a pair of
electrodes. The EL layer may also have a plurality of layers in addition
to the light-emitting layer. The plurality of layers is a combination of
layers that include a substance having a high carrier-injection property
and a substance having a, high carrier-transport property. Those layers
are stacked so that a light-emitting region is formed in a region away
from the electrodes, that is, carriers recombine in a region away from
the electrodes. In this specification, the layer that includes a
substance having a high carrier-injection property or a substance having
a high carrier-transport property is also called a functional layer which
functions, for instance, to inject or transport carriers. As the
functional layer, a hole-injection layer, a hole-transport layer, an
electron-injection layer, an electron-transport layer, or the like can be
used.

[0117] In the light-emitting element of this embodiment illustrated in
FIG. 1A, an EL layer 102 having a light-emitting layer 113 is provided
between a pair of electrodes, a first electrode 101 and a second
electrode 103. The EL layer 102 includes a hole-injection layer 111, a
hole-transport layer 112, the light-emitting layer 113, an
electron-transport layer 114, and an electron-injection layer 115. The
light-emitting element in FIG. 1A includes: the first electrode 101
formed over a substrate 100; the hole-injection layer 111, the
hole-transport layer 112, the light-emitting layer 113, the
electron-transport layer 114, and the electron-injection layer 115 which
are stacked over the first electrode 101 in this order; and the second
electrode 103 provided over the electron-injection layer 115. Note that,
in the light-emitting element described in this embodiment, the first
electrode 101 functions as an anode and the second electrode 103
functions as a cathode.

[0118] The substrate 100 is used as a support of the light-emitting
element. For example, glass, quartz, plastic, or the like can be used for
the substrate 100. Alternatively, a flexible substrate may be used. The
flexible substrate is a substrate that can be bent, such as a plastic
substrate made of polycarbonate, polyarylate, or polyether sulfone, for
example. Alternatively, a film (made of polypropylene, polyester, vinyl,
polyvinyl fluoride, vinyl chloride, or the like), an inorganic film
formed by evaporation, or the like can be used. Note that materials other
than glass and plastic can be used as long as they can function as a
support of the light-emitting element.

[0119] For the first electrode 101, a metal, an alloy, an electrically
conductive compound, a mixture thereof, or the like which has a high work
function (specifically, a work function of 4.0 eV or more) is preferably
used. Specific examples include indium tin oxide (ITO), indium tin oxide
containing silicon or silicon oxide, indium zinc oxide (IZO), indium
oxide containing tungsten oxide and zinc oxide (IWZO), and the like.
Films of these conductive metal oxides are usually formed by sputtering;
however, a sol-gel method or the like may also be used. For example,
indium oxide-zinc oxide (IZO) can be formed by a sputtering method using
a target in which 1 wt % to 20 wt % of zinc oxide is added to indium
oxide. IWZO can be formed by a sputtering method using a target in which
0.5 wt % to 5 wt % of tungsten oxide and 0.1 wt % to 1 wt % of zinc oxide
are added to indium oxide. Further, gold (Au), platinum (Pt), nickel
(Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt
(Co), copper (Cu), palladium (Pd), nitrides of metal materials (e.g.,
titanium nitride), and the like can be given.

[0120] Note that, in the EL layer 102, when a layer in contact with the
first electrode 101 is formed using a composite material in which an
organic compound and an electron acceptor (acceptor) described later are
mixed, the first electrode 101 can be formed using any of a variety of
metals, alloys, and electrically conductive compounds, a mixture thereof,
and the like regardless of the work function. For example, aluminum (Al),
silver (Ag), an alloy containing aluminum (e.g., Al--Si), or the like can
be used.

[0121] The EL layer 102 formed over the first electrode 101 includes at
least the light-emitting layer 113, and part of the EL layer 102 is
formed using the heterocyclic compound which is one embodiment of the
present invention. For the part of the EL layer 102, a known substance
can be used, and either a low molecular compound or a high molecular
compound can be used. Note that the substance used for forming the EL
layer 102 may have not only a structure formed of only an organic
compound but also a structure in which an inorganic compound is partially
contained.

[0122] As illustrated in FIGS. 1A and 1B, the EL layer 102 is formed by
stacking as appropriate the hole-injection layer 111, the hole-transport
layer 112, the electron-transport layer 114, the electron-injection layer
115, and the like in combination as well as the light-emitting layer 113.

[0123] The hole-injection layer 111 includes a substance having a high
hole-injection property. As the substance having a high hole-injection
property, for example, metal oxides such as molybdenum oxide, titanium
oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chromium oxide,
zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten
oxide, and manganese oxide can be used. Alternatively, a
phthalocyanine-based compound such as phthalocyanine (abbreviation:
H2Pc), copper(II) phthalocyanine (abbreviation: CuPc), or vanadyl
phthalocyanine (abbreviation: VOPc) can be used.

[0125] Further alternatively, any of high molecular compounds (e.g.,
oligomers, dendrimers, or polymers) can be used. Examples of the high
molecular compounds include poly(N-vinylcarbazole) (abbreviation: PVK),
poly(4-vinyltriphenylamine) (abbreviation: PVTPA),
poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)met-
hacrylamide] (abbreviation: PTPDMA),
poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation:
Poly-TPD), and the like. Alternatively, a high molecular compound to
which acid is added, such as
poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS),
or polyaniline/poly(styrenesulfonic acid) (PAni/PSS), can be used.

[0126] For the hole-injection layer 111, a composite material in which an
organic compound and an electron acceptor (acceptor) are mixed may be
used. Such a composite material is excellent in a hole-injection property
and a hole-transport property because holes are generated in the organic
compound by the electron acceptor. In this case, the organic compound is
preferably a material excellent in transporting the generated holes (a
substance having a high hole-transport property).

[0127] As the organic compound for the composite material, a variety of
compounds such as an aromatic amine compound, a carbazole derivative,
aromatic hydrocarbon, and a high molecular compound (such as oligomer,
dendrimer, or polymer) can be used. The organic compound used for the
composite material is preferably an organic compound having a high
hole-transport property. Specifically, a substance having a hole mobility
of 10-6 cm2/Vs or more is preferably used. Note that a
substance other than the above may be used as long as it has a
hole-transport property higher than its electron-transport property. The
organic compounds which can be used for the composite material are
specifically shown below.

[0128] For example, as the organic compounds that can be used for the
composite material, there are aromatic amine compounds such as TDATA,
MTDATA, DPAB, DNTPD, DPA3B, PCzPCA1, PCzPCA2, PCzPCN1,
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or
α-NPD), and
N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine
(abbreviation: TPD); and carbazole derivatives such as
4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP),
1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB),
9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), and
1,4-bis[4-(N-carbazolyl)phenyl-2,3,5,6-tetraphenylbenzene.

[0131] As electron acceptors, organic compounds such as
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:
F4-TCNQ) and chloranil, and a transition metal oxide can be given.
In addition, oxides of metals belonging to Groups 4 to 8 in the periodic
table can be also given. Specifically, vanadium oxide, niobium oxide,
tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide,
manganese oxide, and rhenium oxide are preferable since their
electron-accepting property is high. Among these, molybdenum oxide is
especially preferable since it is stable in the air and its hygroscopic
property is low and is easily treated.

[0132] Note that the hole-injection layer 111 may be formed using a
composite material of the above-described high molecular compound, such
as PVK, PVTPA, PTPDMA, or Poly-TPD, and the above-described electron
acceptor.

[0133] The hole-transport layer 112 includes a substance having a high
hole-transport property. The heterocyclic compound of one embodiment of
the present invention described in Embodiment 1 has an excellent
hole-transport property and therefore can be preferably used for the
hole-transport layer 112.

[0134] As the substance having a high hole-transport property, it is
possible to use an aromatic amine compound such as NPB, TPD,
4,4'-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: DFLDPBi), or
4,4'-bis[N-(Spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB), for example. The materials described here are
mainly materials having a hole mobility of 10-6 cm2/Vs or more.
Note that a substance other than the above may be used as long as it has
a hole-transport property higher than its electron-transport property.
The layer containing a substance having a high hole-transport property is
not limited to a single layer, and a stacked layer in which two or more
layers containing the above-described substance are stacked may be used.

[0135] Alternatively, for the hole-transport layer 112, a high molecular
compound such as PVK, PVTPA, PTPDMA, or Poly-TPD can be used.

[0136] The light-emitting layer 113 includes a light-emitting substance.
As the light-emitting substance, for example, a fluorescent compound
which exhibits fluorescence or a phosphorescent compound which exhibits
phosphorescence can be used, other than the heterocyclic compound of one
embodiment of the present invention described in Embodiment 1.

[0137] The phosphorescent compounds that can be used for the
light-emitting layer 113 will be given. Examples of the materials for
blue light emission include
N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine
(abbreviation: YGA2S),
4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine
(abbreviation: YGAPA),
4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBAPA), and the like. In addition, examples of the
materials for green light emission include
N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine
(abbreviation: 2PCAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-ami-
ne (abbreviation: 2PCABPhA),
N-(9,10-diphenyl-2-anthryl)-N,N',N-triphenyl-1,4-phenylenediamine
(abbreviation: 2DPAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylen-
ediamine (abbreviation: 2DPABPhA),
N-[9,10-bis(1,1'-biphenyl-2-yl)]-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenyla-
nthracen-2-amine (abbreviation: 2YGABPhA),
N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), and the like.
Further, examples of the materials for yellow light emission include
rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene
(abbreviation: BPT), and the like. Furthermore, examples of the materials
for red light emission include
N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:
p-mPhTD), 7,14-diphenyl-N,N,N',N-tetrakis(4-methylphenyl)acenaphtho[1,2-a-
]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), and the like.

[0138] In addition, the phosphorescent compounds that can be used for the
light-emitting layer 113 will be given. Examples of the materials for
blue light emission include
bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)tetrakis(1--
pyrazolyl)borate (abbreviation: FIr6),
bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)picolinate
(abbreviation: FIrpic),
bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C2'}iridium(III-
)picolinate (abbreviation: Ir(CF3ppy)2(pic)),
bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)acetylaceto-
nate (abbreviation: Fir(acac)), and the like. Examples of the materials
for green light emission include
tris(2-phenylpyridinato-N,C2')iridium(III) (abbreviation:
Ir(ppy)3),
bis(2-phenylpyridinato-N,C2')iridium(III)acetylacetonate
(abbreviation: Ir(ppy)2(acac)),
bis(1,2-diphenyl-1H-benzimidazolato)iridium(III)acetylacetonate
(abbreviation: Ir(pbi)2(acac)),
bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation:
Ir(bzq)2(acac)), and the like. Examples of the materials for yellow
light emission include
bis(2,4-diphenyl-1,3-oxazolato-N,C2')iridium(III)acetylacetonate
(abbreviation: Ir(dpo)2(acac)),
bis[2-(4'-(perfluorophenylphenyl)pyridinato]iridium(III)acetylacetonate
(abbreviation: Ir(p-PF-ph)2(acac)),
bis(2-phenylbenzothiazolato-N,C2')iridium(III)acetylacetonate
(abbreviation: Ir(bt)2(acac)), and the like. Examples of the
materials for orange light emission include
tris(2-phenylquinolinato-N,C2')iridium(III) (abbreviation:
Ir(pq)3),
bis(2-phenylquinolinato-N,C2')iridium(III)acetylacetonate
(abbreviation: Ir(pq)2(acac)), and the like. Examples of the
materials for red light emission include organometallic complexes such as
bis[2-(2'-benzo[4,5-α]thienyl)pyridinato-N,C3')iridium(III)ace-
tylacetonate (abbreviation: Ir(btp)2(acac)),
bis(1-phenylisoquinolinato-N,C2')iridium(III)acetylacetonate
(abbreviation: Ir(piq)2(acac),
(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)
(abbreviation: Ir(Fdpq)2(acac)), and
2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II)
(abbreviation: PtOEP). Furthermore, since light emission from a rare
earth metal ion (electron transition between different multiplicities)
can be obtained by rare earth metal complexes such as
tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:
Tb(acac)3(Phen)),
tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)
(abbreviation: Eu(DBM)3(Phen)), and
tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(-
III) (abbreviation: Eu(TTA)3(Phen)), such rare earth metal complexes
can be used as a phosphorescent compound.

[0139] Note that the light-emitting layer 113 may have a structure in
which any of the above light-emitting substances (a guest material) is
dispersed in another substance (a host material). By using the
heterocyclic compound of one embodiment of the present invention for the
light-emitting layer 113, the light-emitting layer 113 can be a
light-emitting layer having a high hole-transport property. In the
light-emitting layer 113, the heterocyclic compound of one embodiment of
the present invention described in Embodiment 1 can be used as a host
material, and a guest material which is a light-emitting substance is
dispersed in the heterocyclic compound of Embodiment 1; in this manner,
it is possible to obtain light emission from the guest material.

[0140] When the heterocyclic compound of one embodiment of the present
invention is used as a host material (a substance in which a
light-emitting substance different from the host material is dispersed),
the emission color of the light-emitting substance can be obtained. It is
also possible to obtain the mixed color of the emission color of the
heterocyclic compound of one embodiment of the present invention and the
emission color of the light-emitting substance dispersed in this
heterocyclic compound.

[0141] As the substance in which a light-emitting substance is dispersed,
a variety of substances can be used other than the heterocyclic compound
of one embodiment of the present invention described in Embodiment 1. It
is preferable to use a substance whose lowest unoccupied molecular
orbital (LUMO) level is higher than that of the light-emitting substance
and whose highest occupied molecular orbital (HOMO) level is lower than
that of the light-emitting substance.

[0143] As the substance (host material) in which the light-emitting
substance (guest material) is dispersed, plural kinds of substances can
be used.

[0144] As the light-emitting substance, a high molecular compound can also
be used. Specifically, examples of the materials for blue light emission
include poly(9,9-dioctylfluorene-2,7-diyl) (abbreviation: PFO),
poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,5-dimethoxybenzene-1,4-diyl)]
(abbreviation: PF-DMOP),
poly{(9,9-dioctylfluorene-2,7-diyl)-co-[N,N'-di-(p-butylphenyl)-1,4-diami-
nobenzene]} (abbreviation: TAB-PFH), and the like. Further, examples of
the materials for green light emission include poly(p-phenylenevinylene)
(abbreviation: PPV),
poly[(9,9-dihexylfluorene-2,7-diyl)-alt-co-(benzo[2,1,3]thiadiazole-4,7-d-
iyl)] (abbreviation: PFBT),
poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-all-co-(2-methoxy-5-(2-ethy-
lhexyloxy)-1,4-phenylene)], and the like. Furthermore, examples of the
materials for orange to red light emission include
poly[2-methoxy-5-(2'-ethylhexoxy)-1,4-phenylenevinylene] (abbreviation:
MEH-PPV), poly(3-butylthiophene-2,5-diyl) (abbreviation: R4-PAT),
poly{[9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorenylene]-alt-co-[2,5-bis(N-
,N'-diphenyl amino)-1,4-phenylene]},
poly{[2-methoxy-5-(2-ethylhexyloxy)-1,4-bis(1-cyanovinylenephenylene)]-al-
t-co-[2,5-bis(N,N'-diphenylamino)-1,4-phenylene]} (abbreviation:
CN-PPV-DPD), and the like.

[0145] The electron-transport layer 114 includes a substance having a high
electron-transport property. The electron-transport layer 114 is formed
using, for example, a metal complex having a quinoline skeleton or a
benzoquinoline skeleton such as tris(8-quinolinolato)aluminum
(abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum
(abbreviation: Almq3), bis(10-hydroxybenzo[h]-quinolinato)beryllium
(abbreviation: BeBq2), or
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:
BAlq). Alternatively, a metal complex or the like including an
oxazole-based or thiazole-based ligand, such as
bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)2)
or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:
Zn(BTZ)2) can be used. Other than the metal complexes,
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:
PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole
(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen),
bathocuproine (abbreviation: BCP), or the like can also be used. The
substances described here are mainly materials having an electron
mobility of 10-6 cm2/Vs or more. Further, the
electron-transport layer is not limited to a single layer, and a stacked
layer in which two or more layers containing any of the above-described
substances are stacked may be used.

[0146] The electron-injection layer 115 includes a substance having a high
electron-injection property. For the electron-injection layer 115, an
alkali metal, an alkaline earth metal, or a compound thereof, such as
lithium (Li), cesium (Cs), calcium (Ca), lithium fluoride (LiF), cesium
fluoride (CsF), calcium fluoride (CaF2), or lithium oxide
(LiOx), can be used. Alternatively, a rare earth metal compound like
erbium fluoride (ErF3) can be used. Alternatively, the
above-mentioned substances for forming the electron-transport layer 114
can also be used.

[0147] Alternatively, a composite material in which an organic compound
and an electron donor (donor) are mixed may be used for the
electron-injection layer 115. Such a composite material is excellent in
an electron-injection property and an electron-transport property because
electrons are generated in the organic compound by the electron donor. In
this case, the organic compound is preferably a material excellent in
transporting the generated electrons. Specifically, for example, the
substances for forming the electron-transport layer 114 (e.g., a metal
complex and a heteroaromatic compound), which are described above, can be
used. As the electron donor, a substance showing an electron-donating
property with respect to the organic compound may be used. Specifically,
an alkali metal, an alkaline earth metal, and a rare earth metal are
preferable, and Li, Cs, magnesium (Mg), Ca, erbium (Er), ytterbium (Yb),
and the like are given. In addition, alkali metal oxide or alkaline earth
metal oxide such as lithium oxide, calcium oxide, barium oxide, and the
like can be given. Lewis base such as magnesium oxide can alternatively
be used. An organic compound such as tetrathiafulvalene (abbreviation:
TTF) can alternatively be used.

[0148] Note that each of the above-described hole-injection layer 111,
hole-transport layer 112, light-emitting layer 113, electron-transport
layer 114, and electron-injection layer 115 can be formed by a method
such as an evaporation method (which includes a vacuum evaporation
method), an inkjet method, or a coating method.

[0149] When the second electrode 103 functions as a cathode, it can be
formed using a metal, an alloy, an electrically-conductive compound, a
mixture thereof, or the like having a low work function (preferably, a
work function of 3.8 eV or less). Specifically, Al, Ag, or the like can
be used besides an element belonging to Group 1 or Group 2 of the
periodic table, that is, an alkali metal such Li or Cs and an alkaline
earth metal such as magnesium (Mg), calcium (Ca), or strontium (Sr); an
alloy of the above metals (e.g., Mg--Ag or Al--Li); a rare earth metal
such as europium (Eu) or ytterbium (Yb); an alloy of the above metals, or
the like.

[0150] Note that, in the case where in the EL layer 102, a layer formed in
contact with the second electrode 103 is formed using a composite
material in which the organic compound and the electron donor (donor),
which are described above, are mixed, a variety of conductive materials
such as Al, Ag, ITO, and indium tin oxide containing silicon or silicon
oxide can be used regardless of the work function.

[0151] Note that the second electrode 103 can be formed by a vacuum
evaporation method or a sputtering method. Alternatively, in the case of
using a silver paste or the like, a coating method, an inkjet method, or
the like can be used.

[0152] In the above-described light-emitting element of this embodiment, a
current flows due to a potential difference generated between the first
electrode 101 and the second electrode 103, and holes and electrons
recombine in the EL layer 102, so that light is emitted. Then, this
emitted light is extracted out through one or both of the first electrode
101 and the second electrode 103. Therefore, one of or both the first
electrode 101 and the second electrode 103 is/are an electrode having the
property of transmitting visible light.

[0153] Further, a structure of a layer provided between the first
electrode 101 and the second electrode 103 is not limited to the above
described structure. A structure other than the above may alternatively
be employed as long as a light-emitting region in which holes and
electrons recombine is provided in a portion away from the first
electrode 101 and the second electrode 103 in order to prevent quenching
due to proximity of the light-emitting region to a metal.

[0154] In other words, a layered structure of the layer is not
particularly limited, and a layer formed using a substance having a high
electron-transport property, a substance having a high hole-transport
property, a substance having a high electron-injection property, a
substance having a high hole-injection property, a bipolar substance (a
substance having a high electron-transport property and a high
hole-transport property), a hole blocking material, or the like may
freely be combined with a light-emitting layer including the heterocyclic
compound described in Embodiment 1.

[0155] In a light-emitting element illustrated in FIG. 1B, the EL layer
102 is provided between the first electrode 101 and the second electrode
103 over the substrate 100. The EL layer 102 includes the hole-injection
layer 111, the hole-transport layer 112, the light-emitting layer 113,
the electron-transport layer 114, and the electron-injection layer 115.
The light-emitting element in FIG. 1B includes: the second electrode 103
serving as a cathode over the substrate 100; the electron-injection layer
115, the electron-transport layer 114, the light-emitting layer 113, the
hole-transport layer 112, and the hole-injection layer 111 which are
stacked over the second electrode 103 in this order; and the first
electrode 101 serving as an anode over the hole-injection layer 111.

[0156] A method of forming a light-emitting element will now be
specifically described.

[0157] The light-emitting element of this embodiment has a structure in
which an EL layer is interposed between a pair of electrodes. The EL
layer at least has a light-emitting layer and is formed using the
heterocyclic compound described in Embodiment 1. Further, the EL layer
may include a functional layer (e.g., a hole-injection layer, a
hole-transport layer, an electron-transport layer, or an
electron-injection layer) in addition to the light-emitting layer. Each
electrode (the first electrode or the second electrode), the
light-emitting layer, and each functional layer may be formed by any of
the wet processes such as a droplet discharging method (an inkjet
method), a spin coating method, or a printing method, or by a dry process
such as a vacuum evaporation method, a CVD method, or a sputtering
method. A wet process allows formation at atmospheric pressure with a
simple device and process, thereby having the effects of simplifying the
process and improving the productivity. In contrast, a dry process does
not need dissolution of a material to enable use of a material that has
low solubility in a solution, thereby expanding the range of material
choices.

[0158] All the thin films included in the light-emitting element may be
formed by a wet method. In this case, the light-emitting element can be
manufactured with only facilities needed for a wet process.
Alternatively, formation of the stacked layers up to formation of the
light-emitting layer may be performed by a wet process whereas the
functional layer, the first electrode, and the like which are stacked
over the light-emitting layer may be formed by a dry process. Further
alternatively, the second electrode and the functional layer may be
formed by a dry process before the formation of the light-emitting layer
whereas the light-emitting layer, the functional layer stacked thereover,
and the first electrode may be formed by a wet process. Needless to say,
this embodiment is not limited to this, and the light-emitting element
can be formed by appropriate selection from a wet method and a dry method
depending on a material to be used, necessary film thickness, and the
interface state.

[0159] In this embodiment, the light-emitting element is fabricated over a
substrate made of glass, plastic or the like. By forming a plurality of
such light-emitting elements over one substrate, a passive matrix
light-emitting device can be manufactured. Alternatively, a thin film
transistor (TFT), for instance, may be formed over a substrate formed of
glass, plastic, or the like, and a light-emitting element may be
fabricated over an electrode electrically connected to the TFT; thus, an
active matrix light-emitting device in which the TFT controls the drive
of the light-emitting element can be manufactured. Note that there is no
particular limitation on the structure of the TFT. Either a staggered TFT
or an inverted staggered TFT may be employed. In addition, crystallinity
of a semiconductor used for the TFT is not particularly limited either;
an amorphous semiconductor or a crystalline semiconductor may be used. In
addition, a driver circuit formed over a TFT substrate may be constructed
from both n-channel and p-channel TFTs or from one of n-channel and
p-channel TFTs.

[0160] The heterocyclic compound of one embodiment of the present
invention described in Embodiment 1 has a high hole-transport property
and high emission efficiency. Accordingly, by using the heterocyclic
compound described in Embodiment 1 for a light-emitting element, the
light-emitting element can exhibit high emission efficiency.

[0161] Since the light-emitting element of an embodiment of the present
invention thus obtained has high emission efficiency, a light-emitting
device (such as an image display device) that uses this light-emitting
element can realize low power consumption.

[0162] Note that by use of the light-emitting element described in this
embodiment, a passive matrix light-emitting device or an active matrix
light-emitting device in which the driving of the light-emitting element
is controlled by a TFT can be manufactured.

[0163] In this embodiment, the structures can be combined with those of
the other embodiments, as appropriate.

Embodiment 3

[0164] In Embodiment 3, a mode of a light-emitting element having a
structure in which a plurality of light-emitting units is stacked
(hereinafter, referred to as a stacked-type element) will be described
with reference to FIGS. 2A and 2B. This light-emitting element is a
light-emitting element including a plurality of light-emitting units
between a first electrode and a second electrode.

[0165] In FIG. 2A, a first light-emitting unit 311 and a second
light-emitting unit 312 are stacked between a first electrode 301 and a
second electrode 303. In this embodiment, the first electrode 301
functions as an anode and the second electrode 303 functions as a
cathode. The first electrode 301 and the second electrode 303 can be the
same as those in Embodiment 2. The structures of the first light-emitting
unit 311 and the second light-emitting unit 312 may be the same or
different from each other, and can be the same as those described in
Embodiment 2.

[0166] Further, a charge generating layer 313 is provided between the
first light-emitting unit 311 and the second light-emitting unit 312. The
charge generation layer 313 functions so that electrons are injected into
one light-emitting unit and holes are injected into the other
light-emitting unit by application of a voltage between the first
electrode 301 and the second electrode 303. In this embodiment, when a
voltage is applied to the first electrode 301 so that the potential
thereof is higher than that of the second electrode 303, the charge
generation layer 313 injects electrons into the first light-emitting unit
311 and injects holes into the second light-emitting unit 312.

[0167] Note that the charge generation layer 313 preferably has the
property of transmitting visible light in terms of light extraction
efficiency. Further, the charge generation layer 313 functions even when
it has lower conductivity than the first electrode 301 or the second
electrode 303.

[0168] The charge generation layer 313 may have either a structure
including an organic compound having a high hole-transport property and
an electron acceptor or a structure including an organic compound having
a high electron-transport property and an electron donor. Alternatively,
both of these structures may be stacked.

[0169] In the case where the charge generation layer 313 contains an
electron acceptor and an organic compound having a high hole-transport
property, as the organic compound having a high hole-transport property,
for example, the heterocyclic compound of one embodiment of the present
invention, an aromatic amine compound such as NPB, TPD, TDATA, MTDATA, or
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: B SPB), or the like can be used. The materials described
here are mainly materials having a hole mobility of 10-6 cm2/Vs
or more. Note that a substance other than the above may be used as long
as it is an organic compound having a hole-transport property higher than
its electron-transport property.

[0170] Further, as the electron acceptor,
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:
F4-TCNQ), chloranil, and the like can be given. In addition,
transition metal oxides can be given. Moreover, oxides of metals
belonging to Groups 4 to 8 of the periodic table can be used.
Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium
oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium
oxide are preferable because they have a high electron-accepting
property. Among these metal oxides, molybdenum oxide, which is easy to
handle, is preferred because of its stability in air and low hygroscopic
property.

[0171] On the other hand, in the case where the charge generation layer
313 includes an electron donor and an organic compound having a high
hole-transport property, as the organic compound having a high
electron-transport property, for example, a metal complex having a
quinoline skeleton or a benzoquinoline skeleton, such as Alq, Almq3,
BeBq2, or BAlq, or the like can be used. Alternatively, a metal
complex having an oxazole-based ligand or a thiazole-based ligand, such
as Zn(BOX)2 or Zn(BTZ)2 can be used. Alternatively, in addition
to such a metal complex, PBD, OXD-7, TAZ, BPhen, BCP, or the like can be
used. The materials described here are mainly materials having an
electron mobility of 10-6 cm2/Vs or more. Note that a substance
other than the above may be used as long as it is an organic compound
having an electron-transport property higher than its hole-transport
property.

[0172] Further, as the electron donor, an alkali metal, an alkaline earth
metal, a rare earth metal, a metal belonging to Group 13 of the periodic
table, or an oxide or carbonate thereof can be used. Specifically, Li,
Cs, Mg, Ca, Yb, indium (In), lithium oxide, cesium carbonate, or the like
is preferably used. Alternatively, an organic compound such as
tetrathianaphthacene may be used as the electron donor.

[0173] Note that by formation of the charge generation layer 313 using any
of the above materials, it is possible to suppress an increase in drive
voltage caused by stacking the EL layers.

[0174] In this embodiment, the light-emitting element having two
light-emitting units is described; however, one embodiment of the present
invention can be similarly applied to a light-emitting element in which
three or more light-emitting units are stacked as illustrated in FIG. 2B.
By arrangement of a plurality of light-emitting units, which are
partitioned by the charge-generation layer between a pair of electrodes,
as in the light-emitting element of this embodiment, light emission in a
high luminance region can be achieved with current density kept low.
Thus, its current density can be kept low, so that a light-emitting
element having a long lifetime can be realized.

[0175] With light-emitting units having emission colors different from
each other, the light-emitting element can be made to exhibit light
emission of a desired color as a whole. For example, in a light-emitting
element having two light-emitting units, the emission colors of the first
light-emitting unit and the second light-emitting unit are made
complementary; thus, the light-emitting element which emits white light
as a whole can be obtained. Note that the word "complementary" means
color relationship in which an achromatic color is obtained when colors
are mixed. That is, white light emission can be obtained by mixture of
light obtained from substances emitting the lights of complementary
colors. The same can be applied to a light-emitting element which has
three light-emitting units. For example, the light-emitting element as a
whole can provide white light emission when the emission color of the
first light-emitting unit is red, the emission color of the second
light-emitting unit is green, and the emission color of the third
light-emitting unit is blue.

[0176] Note that this embodiment can be combined with any other embodiment
as appropriate.

Embodiment 4

[0177] In Embodiment 4, a light-emitting device having a light-emitting
element of one embodiment of the present invention will be described with
reference to FIGS. 3A and 3B. FIG. 3A is a top view illustrating a
light-emitting device while FIG. 3B is a cross-sectional view taken along
lines A-B and C-D of FIG. 3A.

[0179] Note that a lead wiring 408 is a wiring for transmitting signals
that are to be inputted to the source side driver circuit 401 and the
gate side driver circuit 403, and receives a video signal, a clock
signal, a start signal, a reset signal, and the like from a flexible
printed circuit (FPC) 409 which serves as an external input terminal.
Although only the FPC is illustrated here, a printed wiring board (PWB)
may be attached to the FPC. The light-emitting device in this
specification includes not only a light-emitting device itself but also a
light-emitting device to which an FPC or a PWB is attached.

[0180] Next, a cross-sectional structure will be described with reference
to FIG. 3B. The driver circuit portion and the pixel portion are formed
over an element substrate 410. In this case, one pixel in the pixel
portion 402 and the source side driver circuit 401 which is the driver
circuit portion are illustrated.

[0181] A CMOS circuit, which is a combination of an n-channel TFT 423 with
a p-channel TFT 424, is formed as the source side driver circuit 401.
Such a driver circuit may be any of a variety of circuits formed using
TFTs, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit.
Although a driver-integrated type in which a driver circuit is formed
over the substrate is described in this embodiment, the present invention
is not limited to this type, and the driver circuit can be formed outside
the substrate.

[0182] The pixel portion 402 includes a plurality of pixels having a
switching TFT 411, a current control TFT 412, and a first electrode 413
electrically connected to a drain of the current control TFT 412. Note
that an insulator 414 is formed to cover an end portion of the first
electrode 413. Here, the insulator 414 is formed using a positive type
photosensitive acrylic resin film.

[0183] In order to improve the coverage, the insulator 414 is provided
such that either an upper end portion or a lower end portion of the
insulator 414 has a curved surface with a curvature. For example, when
positive photosensitive acrylic is used as a material for the insulator
414, only an upper end portion of the insulator 414 can have a curved
surface with a radius of curvature (0.2 μm to 3 μm). Alternatively,
the insulator 414 can be formed using either a negative type that becomes
insoluble in an etchant by light irradiation or a positive type that
becomes soluble in an etchant by light irradiation.

[0184] A light-emitting layer 416 and a second electrode 417 are formed
over the first electrode 413. Here, as a material for forming the first
electrode 413 functioning as the anode, it is preferable to use a
material having a high work function. For example, a single layer of an
ITO film, an indium tin oxide film that includes silicon, an indium oxide
film that includes 2 wt % to 20 wt % of zinc oxide (ZnO), a titanium
nitride film, a Cr film, a W film, a (zinc) Zn film, a Pt film, or the
like, a stacked layer of a titanium nitride film and a film that mainly
includes aluminum, a three-layer structure of a titanium nitride film, a
film that mainly includes aluminum and a titanium nitride film, or the
like can be used. Note that, when a stacked structure is employed,
resistance of a wiring is low and a favorable ohmic contact is obtained.

[0185] In addition, the light-emitting layer 416 is formed by any of
various methods such as an evaporation method using an evaporation mask,
a droplet discharging method like an inkjet method, a printing method,
and a spin coating method. The light-emitting layer 416 includes the
heterocyclic compound described in Embodiment 1. Further, the
light-emitting layer 416 may include another material such as a low
molecular material, an oligomer, a dendrimer, or a high molecular
material.

[0186] As a material used for the second electrode 417 which is formed
over the light-emitting layer 416 and serves as a cathode, it is
preferable to use a material having a low work function (e.g., Al, Mg,
Li, Ca, or an alloy or compound thereof such as MgAg, Mg--In, Al--Li,
LiF, or CaF2). In the case where light generated in the
light-emitting layer 416 is transmitted through the second electrode 417,
the second electrode 417 may be formed of a stack of a metal thin film
having a reduced thickness and a transparent conductive film (e.g., ITO,
indium oxide containing 2 wt % to 20 wt % of zinc oxide, indium tin oxide
containing silicon or silicon oxide, or zinc oxide (ZnO)).

[0187] The sealing substrate 404 is attached to the element substrate 410
with the sealant 405; thus, a light-emitting element 418 is provided in
the space 407 enclosed by the element substrate 410, the sealing
substrate 404, and the sealant 405. Note that the space 407 is filled
with a filler such as an inert gas (e.g., nitrogen or argon) or the
sealant 405.

[0188] Note that as the sealant 405, an epoxy-based resin is preferably
used. A material used for these is desirably a material which does not
transmit moisture or oxygen as possible. As a material for the sealing
substrate 404, a glass substrate, a quartz substrate, or a plastic
substrate including fiberglass-reinforced plastics (FRP), polyvinyl
fluoride (PVF), polyester, acrylic, or the like can be used.

[0189] As described above, the active matrix light-emitting device having
the light-emitting element of one embodiment of the present invention can
be obtained.

[0190] Further, the light-emitting element of the present invention can be
used for a passive matrix light-emitting device as well as the above
active matrix light-emitting device. FIGS. 4A and 4B illustrate a
perspective view and a cross-sectional view of a passive matrix
light-emitting device using the light-emitting element of the present
invention. FIG. 4A is a perspective view of the light-emitting device,
and FIG. 4B is a cross-sectional view taken along line X-Y of FIG. 4A.

[0191] In FIGS. 4A and 4B, an EL layer 504 is provided between a first
electrode 502 and a second electrode 503 over a substrate 501. An end
portion of the first electrode 502 is covered with an insulating layer
505. In addition, a partition layer 506 is provided over the insulating
layer 505. The sidewalls of the partition layer 506 are aslope so that a
distance between both sidewalls is gradually narrowed toward the surface
of the substrate. In other words, a cross section taken along the
direction of the short side of the partition layer 506 is trapezoidal,
and the lower side (a side in contact with the insulating layer 505) is
shorter than the upper side (a side not in contact with the insulating
layer 505). By provision of the partition layer 506 in such a manner, a
defect of the light-emitting element due to static electricity or the
like can be prevented.

[0192] Thus, the passive matrix light-emitting device having the
light-emitting element of one embodiment of the present invention can be
obtained.

[0193] The light-emitting devices described in this embodiment (the active
matrix light-emitting device and the passive matrix light-emitting
device) are both formed using the light-emitting element of one
embodiment of the present invention, thereby having high emission
efficiency.

[0194] Note that in this embodiment, an appropriate combination of the
structures described in any other embodiment can be used.

Embodiment 5

[0195] Embodiment 5 will show electronic devices and lighting devices
including the light-emitting device of one embodiment of the present
invention described in Embodiment 4 as a part. Examples of the electronic
devices include cameras such as video cameras and digital cameras, goggle
type displays, navigation systems, audio reproducing devices (e.g., car
audio systems and audio systems), computers, game machines, portable
information terminals (e.g., mobile computers, cellular phones, portable
game machines, and electronic book readers), image reproducing devices in
which a recording medium is provided (specifically, devices that are
capable of reproducing recording media such as digital versatile discs
(DVDs) and provided with a display device that can display an image), and
the like. Specific examples of these electronic devices are shown in
FIGS. 5A to 5D.

[0196] FIG. 5A illustrates a television set according to one embodiment of
the present invention, which includes a housing 611, a supporting base
612, a display portion 613, speaker portions 614, video input terminals
615, and the like. In this television set, the light-emitting device of
one embodiment of the present invention can be applied to the display
portion 613. Since the light-emitting device of one embodiment of the
present invention has high emission efficiency, a television set with low
power consumption can be obtained by application of the light-emitting
device of one embodiment of the present invention.

[0197] FIG. 5B illustrates a computer according to one embodiment of the
present invention, which includes a main body 621, a housing 622, a
display portion 623, a keyboard 624, an external connection port 625, a
pointing device 626, and the like. In this computer, the light-emitting
device of the present invention can be applied to the display portion
623. Since the light-emitting device of one embodiment of the present
invention has high emission efficiency, a computer with low power
consumption can be obtained by application of the light-emitting device
of one embodiment of the present invention.

[0198] FIG. 5C shows a cellular phone of one embodiment of the present
invention, which includes a main body 631, a housing 632, a display
portion 633, an audio input portion 634, an audio output portion 635,
operation keys 636, an external connection port 637, an antenna 638, and
the like. In this cellular phone, the light-emitting device of the
present invention can be applied to the display portion 633. Since the
light-emitting device of one embodiment of the present invention has high
emission efficiency, a cellular phone having reduced power consumption
can be obtained by application of the light-emitting device of one
embodiment of the present invention.

[0199] FIG. 5D shows a camera of one embodiment of the present invention,
which includes a main body 641, a display portion 642, a housing 643, an
external connection port 644, a portion 645 for receiving signals from a
remote control, an image receiving portion 646, a battery 647, an audio
input portion 648, operation keys 649, an eyepiece portion 650, and the
like. In this camera, the light-emitting device of one embodiment of the
present invention can be applied to the display portion 642. Since the
light-emitting device of one embodiment of the present invention has high
emission efficiency, a camera having reduced power consumption can be
obtained by application of the light-emitting device of one embodiment of
the present invention.

[0200] As thus described, application range of the light-emitting device
of one embodiment of the present invention is quite wide, and this
light-emitting device can be applied to electronic devices of a variety
of fields. With use of the light-emitting device of one embodiment of the
present invention, an electronic device having reduced power consumption
can be obtained.

[0201] Moreover, the light-emitting device of one embodiment of the
present invention can be used as a lighting device. FIG. 6 illustrates an
example of a liquid crystal display device using the light-emitting
device of one embodiment of the present invention as a backlight. The
liquid crystal display device illustrated in FIG. 6 includes a housing
701, a liquid crystal layer 702, a backlight 703, and a housing 704. The
liquid crystal layer 702 is connected to a driver IC 705. The
light-emitting device of one embodiment of the present invention is used
as the backlight 703, and a current is supplied through a terminal 706.

[0202] By using the light-emitting device of one embodiment of the present
invention as a backlight of a liquid crystal display device as described
above, a backlight having low power consumption can be obtained.
Moreover, since the light-emitting device of one embodiment of the
present invention is a lighting device for surface light emission and the
enlargement of the light-emitting device is possible, the backlight can
be made larger. Accordingly, a larger-area liquid crystal display device
having low power consumption can be obtained.

[0203] FIG. 7 illustrates an example in which the light-emitting device of
one embodiment of the present invention is used for a desk lamp which is
a lighting device. The desk lamp in FIG. 7 has a housing 801 and a light
source 802, and the light-emitting device of one embodiment of the
present invention is used as the light source 802. The light-emitting
device of one embodiment of the present invention has the light-emitting
element having high emission efficiency and therefore can be used for a
desk lamp having low power consumption.

[0204] FIG. 8 illustrates an example in which the light-emitting device of
one embodiment of the present invention is used for an indoor lighting
device 901. Since the light-emitting device of an embodiment of the
present invention can have a larger area, the light-emitting device of an
embodiment of the present invention can be used as a lighting system
having a large area. Further, the light-emitting device of one embodiment
of the present invention has the light-emitting element having high
emission efficiency and therefore can be used as a lighting device having
low power consumption. In a room where the light-emitting device of one
embodiment of the present invention is used as the indoor lighting device
901 as above, a television set 902 of one embodiment of the present
invention as described referring to FIG. 5A can be installed so that
pubic broadcasting and movies can be watched.

[0205] Note that the structure described of this embodiment can be
implemented in combination with any of the structures described in other
embodiments as appropriate.

Example 1

Synthesis Example 1

[0206] This example will show a method of synthesizing
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA-II) represented by the following Structural formula (100).

##STR00073##

[0207] The method of synthesizing 2mDBFPPA-II is represented by Synthesis
Scheme (C-1), and reaction in the synthesis will be detailed below.

##STR00074##

[0208] In a 100 mL three-neck flask were put 1.2 g (3.0 mmol) of
2-bromo-9,10-diphenylanthracene, 0.87 g (3.0 mmol) of
3-(dibenzofuran-4-yl)phenylboronic acid, and 0.23 g (0.75 mmol) of
tri(ortho-tolyl)phosphine. The air in the flask was replaced with
nitrogen. To this mixture were added 15 mL of toluene, 5.0 mL of ethanol,
and 3.0 mL of a 2.0 mol/L aqueous solution of potassium carbonate. While
the pressure was reduced, this mixture was stirred to be degassed.

[0209] Then, 34 mg (0.15 mmol) of palladium(II) acetate was added to this
mixture, and the mixture was stirred under a nitrogen stream at
80° C. for 4 hours. Then, the aqueous layer of this mixture was
extracted with ethyl acetate, and the extracted solution and the organic
layer were combined and washed with saturated brine. The organic layer
was dried with magnesium sulfate. Then, this mixture was gravity
filtered. The resulting filtrate was concentrated to give a solid, and
the solid was purified by silica gel column chromatography. The
chromatography was carried out using a mixed solvent having a 5:1 ratio
of hexane to toluene as a developing solvent, whereby a solid was
obtained. Recrystallization of the solid from a mixed solvent of toluene
and hexane gave 1.4 g of a yellow powder in 79% yield, which was the
substance to be produced.

[0210] By a train sublimation method, 1.4 g of the obtained yellow
powdered solid was purified. In the purification, the yellow powdered
solid was heated at 270° C. under a pressure of 3.0 Pa with a flow
rate of argon gas of 4.0 mL/min. After the purification, 1.1 g of a
yellow solid was obtained in a yield of 81%, which was the substance to
be produced.

[0211] A nuclear magnetic resonance (NMR) method identified this compound
as 4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA-II), which was the substance to be produced.

[0213] FIGS. 9A and 9B show the 1H NMR charts. Note that FIG. 9B is a
chart showing an enlarged part of FIG. 9A in the range of 7.2 to 8.2 ppm.

[0214] Thermogravimetry-differential thermal analysis (TG-DTA) of
2mDBFPPA-II, which was obtained, was performed. A high vacuum
differential type differential thermal balance (manufactured by Bruker
AXS K.K., TG/DTA 2410SA) was used for the measurement. The measurement
was carried out under a nitrogen stream (a flow rate of 200 mL/min) and a
normal pressure at a temperature rising rate of 10° C./min. The
relationship between weight and temperature (thermogravimetry)
demonstrates that the temperature at which the weight at the start of the
measurement is reduced by 5% (5% weight loss temperature) is
418.0° C., which is indicative of high heat resistance.

[0215] Further, FIG. 10A shows an absorption spectrum of a toluene
solution of 2mDBFPPA-II, and FIG. 10B shows an emission spectrum thereof.
FIG. 11A shows an absorption spectrum of a thin film of 2mDBFPPA-II, and
FIG. 11B shows an emission spectrum thereof. The absorption spectrum was
measured using an ultraviolet-visible spectrophotometer (V-550, produced
by JASCO Corporation). The measurements were performed with samples
prepared in such a manner that the solution was put in a quartz cell
while the thin film was obtained by evaporation onto a quartz substrate.
The absorption spectrum of the solution was obtained by subtracting the
absorption spectra of quartz and toluene from those of quartz and the
solution, and the absorption spectrum of the thin film was obtained by
subtracting the absorption spectrum of a quartz substrate from those of
the quartz substrate and the thin film. In FIGS. 10A and 10B and FIGS.
11A and 11B, the horizontal axis represents wavelength (nm) and the
vertical axis represents intensity (arbitrary unit). In the case of the
toluene solution, absorption was observed at around 406 nm, and the
emission wavelengths were 424 nm and 447 nm (excitation wavelength: 384
nm). In the case of the thin film, absorption was observed at around 246
nm, 289 nm, 371 nm, 391 nm and 413 nm, and the emission wavelengths were
437 nm and 458 nm (excitation wavelength: 392 nm).

[0216] The HOMO level and the LUMO level of the thin film of 2mDBFPPA-II
were measured. The value of the HOMO level was obtained by conversion of
a value of the ionization potential measured with a photoelectron
spectrometer (AC-2, manufactured by Riken Keiki Co., Ltd.) in the
atmosphere into a negative value. The value of the LUMO level was
obtained in such a manner that the absorption edge, which was obtained
from Tauc plot with an assumption of direct transition using data on the
absorption spectrum of the thin film of 2mDBFPPA-II which is shown in
FIG. 11A, was regarded as an optical energy gap and added to the value of
the HOMO level. As a result, the HOMO level and LUMO level of 2mDBFPPA-II
were found to be -5.66 eV and -2.79 eV, respectively.

[0217] The oxidation characteristic and reduction characteristic of
2mDBFPPA-II were measured. In the measurements of the oxidation and
reduction characteristics, cyclic voltammetry (CV) measurement was
employed, and an electrochemical analyzer (ALS model 600A, manufactured
by BAS Inc.) was used.

[0218] As a solution used in the CV measurement, dehydrated
N,N-dimethylformamide (DMF, product of Sigma-Aldrich Inc., 99.8%, catalog
No. 22705-6) was used as a solvent, and tetra-n-butylammonium perchlorate
(n-Bu4NClO4, product of Tokyo Chemical Industry Co., Ltd.,
catalog No. T0836), which was a supporting electrolyte, was dissolved in
the solvent such that the concentration of tetra-n-butylammonium
perchlorate was 100 mmol/L. Further, the object to be measured was
dissolved in the solvent such that the concentration thereof was 1
mmol/L. A platinum electrode (manufactured by BAS Inc., PTE platinum
electrode) was used as a working electrode, a platinum electrode
(manufactured by BAS Inc., Pt counter electrode for VC-3, (5 cm)) was
used as an auxiliary electrode, and an Ag/Ag.sup.+ electrode
(manufactured by BAS Inc., RE-5 reference electrode for nonaqueous
solvent) was used as a reference electrode. Note that the measurement was
conducted at room temperature. In addition, the scan rate at the CV
measurement was set to 0.1 V/s in all the measurement.

[0219] The reduction characteristic of 2mDBFPPA-II was examined by 100
measurement cycles in which the potential of the working electrode with
respect to the reference electrode was scanned from -1.48 V to -2.27 V
and then from -2.27 V to -1.48 V in each cycle. Similarly, the oxidation
characteristic of 2mDBFPPA-II was evaluated by 100 measurement cycles in
which the potential of the working electrode with respect to the
reference electrode was scanned from 0.18 V to 1.02 V and then from 1.02
V to 0.18 V in each cycle.

[0220] According to the measurement results, a peak current corresponding
to oxidation at around 0.89 V (vs. Ag/Ag.sup.+) and a peak current
corresponding to reduction at around -2.16 V (vs. Ag/Ag.sup.+) were
observed. FIG. 12 shows a graph of the results.

[0221] Even after as many as 100 scan cycles, 2mDBFPPA-II showed no
significant change in the peak position of the CV curves representing
oxidation and reduction and kept the peak intensity at 76% of the initial
intensity on the oxidation side and at 90% on the reduction side. Thus,
it is understood that 2mDBFPPA-II is relatively stable, when subjected to
repetitions of oxidation from a neutral state to an oxidized state and
reduction from the oxidized state to the neutral state or repetitions of
reduction from a neutral state to a reduced state and oxidation from the
reduced state to the neutral state.

Example 2

Synthesis Example 2

[0222] This example will show a method of synthesizing
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene (abbreviation:
2mDBTPPA-II) represented by the following Structural formula (300).

##STR00075##

[0223] The method of synthesizing 2mDBTPPA-II is represented by Synthesis
Scheme (D-1), and reaction in the synthesis will be detailed below.

##STR00076##

[0224] In a 100 mL three-neck flask were put 1.6 g (4.0 mmol) of
2-bromo-9,10-diphenylanthracene, 1.2 g (4.0 mmol) of
3-(dibenzothiophen-4-yl)phenylboronic acid, and 0.30 g (1.0 mmol) of
tri(ortho-tolyl)phosphine. The air in the flask was replaced with
nitrogen. To this mixture were added 25 mL of toluene, 5.0 mL of ethanol,
and 5.0 mL of a 2.0 mol/L aqueous solution of potassium carbonate. While
the pressure was reduced, this mixture was stirred to be degassed.

[0225] Then, 45 mg (0.20 mmol) of palladium(II) acetate was added to this
mixture, and the mixture was stirred under a nitrogen stream at
80° C. for 5 hours. Then, the aqueous layer of this mixture was
extracted with toluene, and the toluene solution and the organic layer
were combined and washed with saturated brine. The organic layer was
dried with magnesium sulfate. Then, this mixture was gravity filtered.
The resulting filtrate was concentrated to give an oily substance. The
obtained oily substance was purified by silica gel column chromatography.
The chromatography was carried out using a mixed solvent having a 5:1
ratio of hexane to toluene as a developing solvent, whereby a solid was
obtained. Recrystallization of the solid from a mixed solvent of toluene
and hexane gave 1.6 g of a yellow powder in 70% yield, which was the
substance to be produced.

[0226] By a train sublimation method, 1.6 g of the obtained yellow
powdered solid was purified. In the purification, the yellow powdered
solid was heated at 290° C. under a pressure of 3.0 Pa with a flow
rate of argon gas of 4.0 mL/min. After the purification, 1.4 g of a
yellow solid was obtained in a yield of 87%, which was the substance to
be produced.

[0227] A nuclear magnetic resonance (NMR) method identified this compound
as 4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene (abbreviation:
2mDBTPPA-II), which was the substance to be produced.

[0229] FIGS. 13A and 13B show the 1H NMR charts. Note that FIG. 13B
is a chart showing an enlarged part of FIG. 13A in the range of 7.2 to
8.3 ppm.

[0230] Thermogravimetry-differential thermal analysis (TG-DTA) of
2mDBTPPA-II, which was obtained, was performed. A high vacuum
differential type differential thermal balance (manufactured by Bruker
AXS K.K., TG/DTA 2410SA) was used for the measurement. The measurement
was carried out under a nitrogen stream (a flow rate of 200 mL/min) and a
normal pressure at a temperature rising rate of 10° C./min. The
relationship between weight and temperature (thermogravimetiy)
demonstrates that the 5% weight loss temperature is 441.1° C.,
which is indicative of high heat resistance.

[0231] Further, FIG. 14A shows an absorption spectrum of a toluene
solution of 2mDBTPPA-II, and FIG. 14B shows an emission spectrum thereof.
FIG. 15A shows an absorption spectrum of a thin film of 2mDBTPPA-II, and
FIG. 15B shows an emission spectrum thereof. The absorption spectrum was
measured using an ultraviolet-visible spectrophotometer (V-550, produced
by JASCO Corporation). The measurements were performed with samples
prepared in such a manner that the solution was put in a quartz cell
while the thin film was obtained by evaporation onto a quartz substrate.
The absorption spectrum of the solution was obtained by subtracting the
absorption spectra of quartz and toluene from those of quartz and the
solution, and the absorption spectrum of the thin film was obtained by
subtracting the absorption spectrum of a quartz substrate from those of
the quartz substrate and the thin film. In FIGS. 14A and 14B and FIGS.
15A and 15B, the horizontal axis represents wavelength (nm) and the
vertical axis represents intensity (arbitrary unit). In the case of the
toluene solution, absorption was observed at around 407 nm, and the
emission wavelengths were 423 nm and 446 nm (excitation wavelength: 385
nm). In the case of the thin film, absorption was observed at around 244
nm, 293 nm, 371 nm, 392 nm and 414 nm, and the emission wavelengths were
437 nm and 459 nm (excitation wavelength: 391 nm).

[0232] The HOMO level and the LUMO level of the thin film of 2mDBTPPA-II
were measured. The value of the HOMO level was obtained by conversion of
a value of the ionization potential measured with a photoelectron
spectrometer (AC-2, manufactured by Riken Keiki Co., Ltd.) in the
atmosphere into a negative value. The value of the LUMO level was
obtained in such a manner that the absorption edge, which was obtained
from Tauc plot with an assumption of direct transition using data on the
absorption spectrum of the thin film of 2mDBTPPA-II which is shown in
FIG. 15A, was regarded as an optical energy gap and added to the value of
the HOMO level. As a result, the HOMO level and LUMO level of 2mDBTPPA-II
were found to be -5.71 eV and -2.85 eV, respectively.

[0233] The oxidation characteristic and reduction characteristic of
2mDBTPPA-II were measured. In the measurements of the oxidation and
reduction characteristics, cyclic voltammetry (CV) measurement was
employed, and an electrochemical analyzer (ALS model 600A, manufactured
by BAS Inc.) was used.

[0234] As a solution used in the CV measurement, dehydrated
N,N-dimethylformamide (DMF, product of Sigma-Aldrich Inc., 99.8%, catalog
No. 22705-6) was used as a solvent, and tetra-n-butylammonium perchlorate
(n-Bu4NClO4, product of Tokyo Chemical Industry Co., Ltd.,
catalog No. T0836), which was a supporting electrolyte, was dissolved in
the solvent such that the concentration of tetra-n-butylammonium
perchlorate was 100 mmol/L. Further, the object to be measured was
dissolved in the solvent such that the concentration thereof was 1
mmol/L. A platinum electrode (manufactured by BAS Inc., PTE platinum
electrode) was used as a working electrode, a platinum electrode
(manufactured by BAS Inc., Pt counter electrode for VC-3, (5 cm)) was
used as an auxiliary electrode, and an Ag/Ag.sup.+ electrode
(manufactured by BAS Inc., RE-5 reference electrode for nonaqueous
solvent) was used as a reference electrode. Note that the measurement was
conducted at room temperature. In addition, the scan rate at the CV
measurement was set to 0.1 V/s in all the measurement.

[0235] The reduction characteristic of 2mDBTPPA-II was examined by 100
measurement cycles in which the potential of the working electrode with
respect to the reference electrode was scanned from -1.46 V to -2.25 V
and then from -2.25 V to -1.46 V in each cycle. Similarly, the oxidation
characteristic of 2mDBTPPA-II was evaluated by 100 measurement cycles in
which the potential of the working electrode with respect to the
reference electrode was scanned from 0.32 V to 1.00 V and then from 1.00
V to 0.32 V in each cycle.

[0236] According to the measurement results, a peak current corresponding
to oxidation at around 0.88 V (vs. Ag/Ag.sup.+) and a peak current
corresponding to reduction at around -2.16 V (vs. Ag/Ag.sup.+) were
observed. FIG. 16 shows a graph of the results.

[0237] Even after as many as 100 scan cycles, 2mDBTPPA-II showed no
significant change in the peak position of the CV curves representing
oxidation and reduction and kept the peak intensity at 76% of the initial
intensity on the oxidation side and at 90% on the reduction side. Thus,
it is understood that 2mDBTPPA-II is relatively stable, when subjected to
repetitions of oxidation from a neutral state to an oxidized state and
reduction from the oxidized state to the neutral state or repetitions of
reduction from a neutral state to a reduced state and oxidation from the
reduced state to the neutral state.

Example 3

[0238] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37A. Chemical
formulae of materials used in this example are shown below.

##STR00077## ##STR00078##

[0239] Methods of fabricating Light-emitting Element 1 of this example and
Reference Light-emitting Element 1 will now be described.

(Light-Emitting Element 1)

[0240] First, indium tin oxide containing silicon oxide (ITSO) was
deposited by a sputtering method on a glass substrate 1100, whereby a
first electrode 1101 was formed. Its thickness was 110 nm and the
electrode area was 2 mm×2 mm. Here, the first electrode 1101 is an
electrode that functions as an anode of the light-emitting element.

[0241] Next, as pretreatment for forming the light-emitting element over
the substrate 1100, a surface of the substrate was washed with water,
baked at 200° C. for one hour, and subjected to UV ozone treatment
for 370 seconds.

[0242] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10-4 Pa, and subjected to vacuum baking at 170°
C. for 30 minutes in a heating chamber of the vacuum evaporation
apparatus, and then the substrate 1100 was cooled down for about 30
minutes.

[0243] Next, the substrate 1100 was fixed to a substrate holder in a
vacuum evaporation apparatus so that a surface of the substrate 1100 on
which the first electrode 1101 was formed faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10-4 Pa. Then,
by an evaporation method using resistance heating,
9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA) which
is a substance having a high hole-transport property and molybdenum(VI)
oxide which is an acceptor substance were co-evaporated to form a
hole-injection layer 1111 over the first electrode 1101. The thickness of
the hole-injection layer 1111 was 50 nm, and the weight ratio of CzPA to
molybdenum(VI) oxide was controlled to be 4:2 (=CzPA:molybdenum(VI)
oxide). Note that the co-evaporation method refers to an evaporation
method in which evaporation is carried out from a plurality of
evaporation sources at the same time in one treatment chamber.

[0244] Next, 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine
(abbreviation: BPAFLBi) was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby a hole-transport layer 1112 was
formed.

[0245] Furthermore, 2mDBFPPA-II synthesized in Example 1 and
4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBAPA) were co-evaporated to form a light-emitting layer
1113 over the hole-transport layer. The weight ratio of 2mDBFPPA-II to
PCBAPA was adjusted to 1:0.1 (=2mDBFPPA-II:PCBAPA). The thickness of the
light-emitting layer 1113 was set to 30 nm.

[0246] Then, over the light-emitting layer 1113, a 10 nm thick layer of
tris(8-quinolinolato)aluminum(III) (abbreviation: Alq) and, a 15 nm thick
layer of bathophenanthroline (abbreviation: BPhen) were deposited on the
Alq layer, whereby an electron-transport layer 1114 including Alq and
BPhen was obtained.

[0247] Further, a 1 nm thick film of lithium fluoride (LiF) was formed
over the electron-transport layer 1114 by evaporation, whereby an
electron-injection layer 1115 was formed.

[0248] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 1 of this example was fabricated.

[0249] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

(Reference Light-Emitting Element 1)

[0250] The light-emitting layer 1113 of Reference Light-emitting Element 1
was formed by co-evaporation of
4-[4-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2DBFPPA-II) and PCBAPA, instead of the material used for Light-emitting
Element 1. The weight ratio of 2DBFPPA-II and PCBAPA was adjusted to
1:0.1 (=2DBFPPA-II:PCBAPA). The thickness of the light-emitting layer
1113 was set to 30 nm. The layers other than the light-emitting layer
1113 were formed in the same manner as Light-emitting Element 1.

[0252] Light-emitting Element 1 and Reference Light-emitting Element 1
were sealed in a glove box containing a nitrogen atmosphere so as not to
be exposed to air. Then, operation characteristics of the elements were
measured. Note that the measurement was carried out at room temperature
(in the atmosphere kept at 25° C.).

[0254] As seen from FIG. 20 and the CIE chromaticity coordinates in Table
2, blue light emission is shown by Light-emitting Element 1 and Reference
Light-emitting Element 1, which were formed. FIG. 17, FIG. 18, FIG. 19,
and Table 2 reveal that Light-emitting Element 1 exhibits better
chromaticity and higher current efficiency and external quantum
efficiency than those of Reference Light-emitting Element 1.

[0255] As described above, 2mDBFPPA-II produced in Example 1 was used as
the host material of the light-emitting layer, whereby the light-emitting
element achieved good chromaticity and high emission efficiency.

[0256] Next, Light-emitting Element 1 and Reference Light-emitting Element
1 were subjected to reliability tests. Results of the reliability tests
are shown in FIG. 21. In FIG. 21, the vertical axis represents normalized
luminance (%) with an initial luminance of 100%, and the horizontal axis
represents driving time (h) of the elements. In the reliability tests,
Light-emitting Element 1 of this example and Reference Light-emitting
Element 1 were driven under the conditions where the current density was
constant and the initial luminance was 1000 cd/m2. FIG. 21 shows
that Light-emitting Element 1 and Reference Light-emitting Element 1 kept
86% of the initial luminance after the driving for 410 hours. Thus,
Light-emitting Element 1 is equal in reliability to Reference
Light-emitting Element 1 as well as has better chromaticity and higher
emission efficiency than those of Reference Light-emitting Element 1.

[0257] Light-emitting Element 1 exhibited better chromaticity and higher
emission efficiency than those of Reference Light-emitting Element 1. The
difference in host material structure between the light-emitting layers
of Light-emitting Element 1 and Reference Light-emitting Element 1 is
that the 2-position of an anthracene skeleton and the 4-position of a
dibenzofuran skeleton in a dibenzofuran derivative which is the host
material are bonded through a phenylene group at the para-position in
Reference Light-emitting Element 1 while bonded through a phenylene group
at the meta-position in Light-emitting Element 1. Whether what lies
between the 2-position of the anthracene skeleton and the 4-position of
the dibenzofuran skeleton is the phenylene group at the para-position or
that at the meta-position makes a difference in emission efficiency
between Light-emitting Element 1 and Reference Light-emitting Element 1.
This reveals that the dibenzofuran derivative of one embodiment of the
present invention is effective in realizing high emission efficiency, in
respect of its structure where the 2-position of the anthracene skeleton
and the 4-position of the dibenzofuran skeleton are bonded through the
phenylene group at the meta-position. Further, it is understood that, by
using the dibenzofuran derivative of one embodiment of the present
invention in a light-emitting element, the light-emitting element can
provide good chromaticity and high emission efficiency.

Example 4

[0258] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37B.

[0259] Methods of fabricating Light-emitting Element 2 of this example and
Reference Light-emitting Element 2 will now be described. Materials used
in the present example are the same as those used in Example 3, and their
chemical formulae are omitted here.

(Light-Emitting Element 2)

[0260] First, ITSO was deposited over the glass substrate 1100 by a
sputtering method, whereby the first electrode 1101 was formed. Its
thickness was 110 nm and the electrode area was 2 mm×2 mm. Here,
the first electrode 1101 is an electrode that functions as an anode of
the light-emitting element.

[0261] Next, as pretreatment for forming the light-emitting element over
the substrate, a surface of the substrate was washed with water, baked at
200° C. for one hour, and subjected to UV ozone treatment for 370
seconds.

[0262] After that, the substrate was transferred into a vacuum evaporation
apparatus where the pressure had been reduced to approximately 10-4
Pa, and subjected to vacuum baking at 170° C. for 30 minutes in a
heating chamber of the vacuum evaporation apparatus, and then the
substrate was cooled down for about 30 minutes.

[0263] Next, the substrate was fixed to a substrate holder in a vacuum
evaporation apparatus so that a surface of the substrate on which the
first electrode was formed faced downward. The pressure in the vacuum
evaporation apparatus was reduced to about 10-4 Pa. Then, CzPA which
is a substance having a high hole-transport property and molybdenum(VI)
oxide which is an acceptor substance were co-evaporated to form the
hole-injection layer 1111 over the first electrode. The thickness of the
hole-injection layer 1111 was 50 nm, and the weight ratio of CzPA to
molybdenum(VI) oxide was controlled to be 4:2 (=CzPA:molybdenum(VI)
oxide).

[0264] Next, BPAFLBi was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby the hole-transport layer 1112 was
formed.

[0265] Further, PCBAPA was deposited to a thickness of 25 nm over the
hole-transport layer 1112, whereby a first light-emitting layer 1113a was
formed. Then, 2mDBFPPA-II synthesized in Example 1 and PCBAPA were
co-evaporated to form a second light-emitting layer 1113b over the first
light-emitting layer 1113a. The weight ratio of 2mDBFPPA-II to PCBAPA was
adjusted to 1:0.1 (=2mDBFPPA-II:PCBAPA). The thickness of the second
light-emitting layer 1113b was set to 30 nm.

[0266] Then, on the second light-emitting layer 1113b, a 10 nm thick layer
of Alq and, a 15 nm thick layer of BPhen were deposited on the Alq layer,
whereby the electron-transport layer 1114 including Alq and BPhen was
obtained.

[0267] Further, a 1 nm thick film of LiF was formed over the
electron-transport layer 1114 by evaporation, whereby the
electron-injection layer 1115 was formed.

[0268] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 2 of this example was fabricated.

[0269] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

(Reference Light-Emitting Element 2)

[0270] The second light-emitting layer 1113b of Reference Light-emitting
Element 2 was formed by co-evaporation of 2DBFPPA-II and PCBAPA, instead
of the material used for Light-emitting Element 2. The weight ratio of
2DBFPPA-II and PCBAPA was adjusted to 1:0.1 (=2DBFPPA-II:PCBAPA). The
thickness of the second light-emitting layer 1113b was set to 30 nm. The
layers other than the second light-emitting layer 1113b were formed in
the same manner as Light-emitting Element 2.

[0272] Light-emitting Element 2 and Reference Light-emitting Element 2
were sealed in a glove box containing a nitrogen atmosphere so as not to
be exposed to air. Then, operation characteristics of the elements were
measured. Note that the measurement was carried out at room temperature
(in the atmosphere kept at 25° C.).

[0274] As seen from FIG. 25 and the CIE chromaticity coordinates in Table
4, blue light emission is shown by Light-emitting Element 2 and Reference
Light-emitting Element 2, which were formed. FIG. 22, FIG. 23, FIG. 24,
and Table 4 reveal that Light-emitting Element 2 exhibits higher current
efficiency and external quantum efficiency than those of Reference
Light-emitting Element 2.

[0275] As described above, 2mDBFPPA-II produced in Example 1 was used as
the host material of the light-emitting layer, whereby the light-emitting
element achieved high emission efficiency when the light-emitting layer
had a two-layer structure as well.

[0276] Next, Light-emitting Element 2 and Reference Light-emitting Element
2 were subjected to reliability tests. Results of the reliability tests
are shown in FIG. 26. In FIG. 26, the vertical axis represents normalized
luminance (%) with an initial luminance of 100%, and the horizontal axis
represents driving time (h) of the elements. In the reliability tests,
Light-emitting Element 2 of this example and Reference Light-emitting
Element 2 were driven under the conditions where the current density was
constant and the initial luminance was 1000 cd/m2. FIG. 26 shows
that Light-emitting Element 2 and Reference Light-emitting Element 2 kept
91% of the initial luminance after the driving for 170 hours. Thus,
Light-emitting Element 2 is equal in reliability to Reference
Light-emitting Element 2 as well as higher emission efficiency than those
of Reference Light-emitting Element 2. Furthermore, the results of the
reliability tests demonstrate that the light-emitting element to which
one embodiment of the present invention is applied is effective in
realizing a light-emitting element having a long lifetime.

[0277] Light-emitting Element 2 exhibited better chromaticity and higher
emission efficiency than those of Reference Light-emitting Element 2. The
difference in host material structure between the light-emitting layers
of Light-emitting Element 2 and Reference Light-emitting Element 2 is
that the 2-position of an anthracene skeleton and the 4-position of a
dibenzofuran skeleton in a dibenzofuran derivative which is the host
material are bonded through a phenylene group at the para-position in
Reference Light-emitting Element 2 while bonded through a phenylene group
at the meta-position in Light-emitting Element 2. Whether what lies
between the 2-position of the anthracene skeleton and the 4-position of
the dibenzofuran skeleton is the phenylene group at the para-position or
that at the meta-position makes a difference in emission efficiency
between Light-emitting Element 2 and Reference Light-emitting Element 2.
This reveals that the dibenzofuran derivative of one embodiment of the
present invention is effective in realizing high emission efficiency, in
respect of its structure where the 2-position of the anthracene skeleton
and the 4-position of the dibenzofuran skeleton are bonded through the
phenylene group at the meta-position. Further, it is understood that, by
using the dibenzofuran derivative of one embodiment of the present
invention in a light-emitting element, the light-emitting element can
provide good chromaticity and high emission efficiency.

Example 5

[0278] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37A. Chemical
formulae of materials used in this example are shown below. Note that the
materials the chemical formulae of which are described above will be
omitted.

##STR00079##

[0279] A method of fabricating Light-emitting Element 3 of this example
will now be described.

(Light-Emitting Element 3)

[0280] First, ITSO was deposited over the glass substrate 1100 by a
sputtering method, whereby the first electrode 1101 was formed. Its
thickness was 110 nm and the electrode area was 2 mm×2 mm Here, the
first electrode 1101 is an electrode that functions as an anode of the
light-emitting element.

[0281] Next, as pretreatment for forming the light-emitting element over
the substrate 1100, a surface of the substrate was washed with water,
baked at 200° C. for one hour, and subjected to UV ozone treatment
for 370 seconds.

[0282] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10-4 Pa, and subjected to vacuum baking at 170°
C. for 30 minutes in a heating chamber of the vacuum evaporation
apparatus, and then the substrate 1100 was cooled down for about 30
minutes.

[0283] Next, the substrate 1100 was fixed to a substrate holder in a
vacuum evaporation apparatus so that a surface of the substrate 1100 on
which the first electrode 1101 was formed faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10-4 Pa. Then,
by an evaporation method using resistance heating, CzPA which is a
substance having a high hole-transport property and molybdenum(VI) oxide
which is an acceptor substance were co-evaporated to form the
hole-injection layer 1111 over the first electrode 1101. The thickness of
the hole-injection layer 1111 was 50 nm, and the weight ratio of CzPA to
molybdenum(VI) oxide was controlled to be 4:2 (=CzPA:molybdenum(VI)
oxide). Note that the co-evaporation method refers to an evaporation
method in which evaporation is carried out from a plurality of
evaporation sources at the same time in one treatment chamber.

[0284] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine
(abbreviation: BPAFLP) was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby the hole-transport layer 1112 was
formed.

[0285] Further, 2mDBTPPA-II synthesized in Example 2 and PCBAPA were
co-evaporated to form the light-emitting layer 1113 over the
hole-transport layer 1112. The weight ratio of 2mDBTPPA-II to PCBAPA was
adjusted to 1:0.1 (=2mDBTPPA-II:PCBAPA). The thickness of the
light-emitting layer 1113 was set to 30 nm.

[0286] Then, over the light-emitting layer 1113, a 10 nm thick layer of
Alq and, a 15 nm thick layer of BPhen were deposited on the Alq layer,
whereby the electron-transport layer 1114 including Alq and BPhen was
obtained.

[0287] Further, a 1 nm thick film of LiF was formed over the
electron-transport layer 1114 by evaporation, whereby the
electron-injection layer 1115 was formed.

[0288] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 3 of this example was fabricated.

[0289] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

[0291] Light-emitting Element 3 was sealed in a glove box containing a
nitrogen atmosphere so as not to be exposed to air. Then, operation
characteristics of the element were measured. Note that the measurement
was carried out at room temperature (in the atmosphere kept at 25°
C.).

[0293] As seen from FIG. 30 and the CIE chromaticity coordinates in Table
6, blue light emission is shown by Light-emitting Element 3, which was
formed. FIG. 27, FIG. 28, FIG. 29, and Table 6 reveal that Light-emitting
Element 3 exhibits good chromaticity, high current efficiency, and high
external quantum efficiency.

[0294] As described above, 2mDBTPPA-II produced in Example 2 was used as
the host material of the light-emitting layer, whereby the light-emitting
element achieved high emission efficiency.

[0295] Next, Light-emitting Element 3 was subjected to reliability tests.
Results of the reliability tests are shown in FIG. 31. In FIG. 31, the
vertical axis represents normalized luminance (%) with an initial
luminance of 100%, and the horizontal axis represents driving time (h) of
the elements. In the reliability tests, Light-emitting Element 3 of this
example was driven under the conditions where the current density was
constant and the initial luminance was 1000 cd/m2. FIG. 31 shows
that Light-emitting Element 3 kept 80% of the initial luminance after the
driving for 220 hours. Thus, Light-emitting Element 3 shows high
reliability. Furthermore, the results of the reliability tests
demonstrate that the light-emitting element to which one embodiment of
the present invention is applied is effective in realizing a
light-emitting element having a long lifetime.

Example 6

[0296] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37B.

[0297] A method of fabricating Light-emitting Element 4 of this example
will now be described. Materials used in the present example are the same
as those used in Example 5, and their chemical formulae are omitted here.

(Light-Emitting Element 4)

[0298] First, ITSO was deposited over the glass substrate 1100 by a
sputtering method, whereby the first electrode 1101 was formed. Its
thickness was 110 nm and the electrode area was 2 mm×2 mm. Here,
the first electrode 1101 is an electrode that functions as an anode of
the light-emitting element.

[0299] Next, as pretreatment for forming the light-emitting element over
the substrate 1100, a surface of the substrate was washed with water,
baked at 200° C. for one hour, and subjected to UV ozone treatment
for 370 seconds.

[0300] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10-4 Pa, and subjected to vacuum baking at 170°
C. for 30 minutes in a heating chamber of the vacuum evaporation
apparatus, and then the substrate 1100 was cooled down for about 30
minutes.

[0301] Next, the substrate 1100 was fixed to a substrate holder in a
vacuum evaporation apparatus so that a surface of the substrate 1100 on
which the first electrode 1101 was formed faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10-4 Pa. Then,
by an evaporation method using resistance heating, CzPA which is a
substance having a high hole-transport property and molybdenum(VI) oxide
which is an acceptor substance were co-evaporated to form the
hole-injection layer 1111 over the first electrode 1101. The thickness of
the hole-injection layer 1111 was 50 nm, and the weight ratio of CzPA to
molybdenum(VI) oxide was controlled to be 4:2 (=CzPA:molybdenum(VI)
oxide). Note that the co-evaporation method refers to an evaporation
method in which evaporation is carried out from a plurality of
evaporation sources at the same time in one treatment chamber.

[0302] Next, BPAFLP was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby the hole-transport layer 1112 was
formed.

[0303] Further, PCBAPA was deposited to a thickness of 25 nm over the
hole-transport layer 1112, whereby the first light-emitting layer 1113a
was formed. Then, 2mDBTPPA-II synthesized in Example 2 and PCBAPA were
co-evaporated to form the second light-emitting, layer 1113b over the
first light-emitting layer 1113a. The weight ratio of 2mDBTPPA-II to
PCBAPA was adjusted to 1:0.1 (=2mDBTPPA-II:PCBAPA). The thickness of the
second light-emitting layer 1113b was set to 30 nm.

[0304] Then, on the second light-emitting layer 1113b, a 10 nm thick layer
of Alq and, a 15 nm thick layer of BPhen were deposited on the Alq layer,
whereby the electron-transport layer 1114 including Alq and BPhen was
obtained.

[0305] Further, a 1 nm thick film of LiF was formed over the
electron-transport layer 1114 by evaporation, whereby the
electron-injection layer 1115 was formed.

[0306] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 4 of this example was fabricated.

[0307] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

[0309] Light-emitting Element 4 was sealed in a glove box containing a
nitrogen atmosphere so as not to be exposed to air. Then, operation
characteristics of the element were measured. Note that the measurement
was carried out at room temperature (in the atmosphere kept at 25°
C.).

[0311] As seen from in FIG. 35 and the CIE chromaticity coordinates in
Table 8, blue light emission is shown by Light-emitting Element 4, which
was formed. FIG. 32, FIG. 33, FIG. 34, and Table 8 reveal that
Light-emitting Element 4 exhibits good chromaticity, high current
efficiency, and high external quantum efficiency.

[0312] As described above, 2mDBTPPA-II produced in Example 2 was used as
the host material of the light-emitting layer, whereby the light-emitting
element achieved high emission efficiency when the light-emitting layer
had a two-layer structure as well.

[0313] Next, Light-emitting Element 4 was subjected to reliability tests.
Results of the reliability tests are shown in FIG. 36. In FIG. 36, the
vertical axis represents normalized luminance (%) with an initial
luminance of 100%, and the horizontal axis represents driving time (h) of
the elements. In the reliability tests, Light-emitting Element 4 of this
example was driven under the conditions where the current density was
constant and the initial luminance was 1000 cd/m2. FIG. 36 shows
that Light-emitting Element 4 kept 80% of the initial luminance after the
driving for 170 hours. Thus, Light-emitting Element 4 shows high
reliability. Furthermore, the results of the reliability tests
demonstrate that the light-emitting element to which one embodiment of
the present invention is applied is effective in realizing a
light-emitting element having a long lifetime.

Example 7

Synthesis Example 3

[0314] This example will show a method of synthesizing
4-[3-(9,10-diphenyl-2-anthryl)phenyl]-2,8-diphenyldibenzofuran
(abbreviation: 2mDBFPPA-III) represented by Structural formula (147)
described in Embodiment 1.

##STR00080##

Step 1: Synthesis of 2,8-dibromodibenzofuran

[0315] The synthesis scheme of Step 1 is shown in (E-1).

##STR00081##

[0316] In a 500 mL three-neck flask were put 8.4 g (50 mmol) of
dibenzofuran and 100 mL of carbon tetrachloride. A solution prepared by
dissolving 17 g (110 mmol) of bromine in 50 mL of chloroform was dripped
through a dropping funnel into the three-neck flask over about 20
minutes. Then, this solution was stirred at room temperature for 7 days.
After that, this solution was washed with a saturated solution of sodium
hydrogen carbonate, an aqueous solution of sodium thiosulfate and
saturated brine. The organic layer was dried with magnesium sulfate, and
this mixture was gravity filtered. The resulting filtrate was
concentrated, and the obtained solid was recrystallized from chloroform.
Accordingly, 6.4 g of a white powder was obtained in 40% yield, which was
the substance to be produced.

Step 2: Synthesis of 2,8-diphenylbenzofuran

[0317] The synthesis scheme of Step 2 is shown in (E-2).

##STR00082##

[0318] In a 300 mL three-neck flask were put 4.0 g (12 mmol) of
2,8-dibromodibenzofuran, 3.0 g (24 mmol) of phenylboronic acid, and 0.55
g (1.8 mmol) of tri(ortho-tolyl)phosphine. The air in the flask was
replaced with nitrogen. To this mixture were added 45 mL of toluene, 15
mL of ethanol, and 15 mL of an aqueous solution of potassium carbonate
(2.0 mol/L). While the pressure was reduced, this mixture was stirred to
be degassed. Then, 81 mg (0.36 mmol) of palladium(II) acetate was added
to this mixture, and the mixture was stirred under a nitrogen stream at
80° C. for 6 hours. After that, the aqueous layer of this mixture
was extracted with toluene, and the toluene solution and the organic
layer were combined and washed with saturated brine. The organic layer
was dried with magnesium sulfate. Then, this mixture was gravity
filtered. The resulting filtrate was concentrated to give an oily
substance, and the oily substance was dissolved in about 20 mL of
toluene. This solution was suction-filtered through Celite (manufactured
by Wako Pure Chemical Industries, Ltd., Catalog No. 531-16855), alumina,
and Florisil (manufactured by Wako Pure Chemical Industries, Ltd.,
Catalog No. 540-00135). The resulting filtrate was concentrated to give
an oily substance, and a mixed solvent of toluene and hexane was added to
the oily substance. The mixture was irradiated with ultrasonic waves,
whereby a solid was precipitated. This solid was collected by suction
filtration to give 2.4 g of a white powder in 63% yield, which was the
substance to be produced.

Step 3: Synthesis of 2,8-diphenyldibenzofuran-4-boronic acid

[0319] The synthesis scheme of Step 3 is shown in (E-3).

##STR00083##

[0320] In a 200 mL three-neck flask was put 2.4 g (7.5 mmol) of
2,8-diphenyldibenzofuran. The air in the flask was replaced with
nitrogen. To this mixture was added 40 mL of tetrahydrofuran (THF), and
this solution was cooled to -80° C. Then, 5.6 mL (9.0 mmol) of
n-butyllithium (a 1.6 mol/L hexane solution) was dripped into this
solution with a syringe. After that, this solution was stirred for 2
hours while its temperature was returned to room temperature. Then, this
solution was again cooled to -80° C., and 1.7 mL (15 mmol) of
trimethyl borate was added to this solution. This solution was stirred
for 3 days while its temperature was returned to room temperature. After
that, about 30 mL of diluted hydrochloric acid (1.0 mol/L) was added to
this solution, followed by stirring for 1 hour. Then, the aqueous layer
of this mixture was extracted with ethyl acetate, and the ethyl acetate
solution and the organic layer were combined and washed with saturated
brine. The organic layer was dried with magnesium sulfate. Then, this
mixture was gravity filtered. The resulting filtrate was concentrated to
give an oily substance, and a mixed solvent of ethyl acetate and hexane
was added to the oily substance. The mixture was irradiated with
ultrasonic waves, whereby a solid was precipitated. This solid was
collected by suction filtration to give 2.2 g of a white powder in
82%quadrature yield, which was the substance to be produced.

Step 4: Synthesis of 4-(3-bromophenyl)-2,8-diphenyldibenzofuran

[0321] The synthesis scheme of Step 4 is shown in (E-4).

##STR00084##

[0322] In a 100 mL three-neck flask were put 1.7 g (6.0 mmol) of
3-bromoiodobenzene and 2.2 g (6.0 mmol) of
2,8-diphenyldibenzofuran-4-boronic acid. The air in the flask was
replaced with nitrogen. To this mixture were added 30 mL of toluene and
6.0 mL of an aqueous solution of sodium carbonate (2.0 mol/L). While the
pressure was reduced, this mixture was stirred to be degassed. To this
mixture was added 0.35 g (0.30 mmol) of
tetrakis(triphenylphosphine)palladium(0), and the mixture was refluxed at
110° C. for 4 hours. After reaction, the aqueous layer was
extracted with ethyl acetate, and the ethyl acetate solution and the
organic layer were combined and washed with saturated brine. The organic
layer was dried with magnesium sulfate. Then, this mixture was gravity
filtered. The resulting filtrate was concentrated to give an oily
substance, and the oily substance was dissolved in about 10 mL of
toluene. This solution was suction-filtered through Celite (manufactured
by Wako Pure Chemical Industries, Ltd., Catalog No. 531-16855), alumina,
and Florisil (manufactured by Wako Pure Chemical Industries, Ltd.,
Catalog No. 540-00135). The resulting filtrate was concentrated to give
an oily substance, and hexane was added to the oily substance. The
mixture was irradiated with ultrasonic waves, whereby a solid was
precipitated. This solid was collected by suction filtration to give 1.2
g of a white powder in 44% yield, which was the substance to be produced.

[0324] In a 50 mL three-neck flask was put 1.2 g (2.5 mmol) of
4-(3-bromophenyl)-2,8-diphenyldibenzofuran. The air in the flask was
replaced with nitrogen. To this mixture was added 15 mL of
tetrahydrofuran (THF), and this solution was cooled to -80° C.
Then, 1.9 mL (3.0 mmol) of n-butyllithium (a 1.6 mol/L hexane solution)
was dripped into this solution with a syringe. After that, this solution
was stirred at the same temperature for 1 hour. Then, 0.56 L (5.0 mmol)
of trimethyl borate was added to this solution, and the mixture was
stirred for 18 hours while its temperature was returned to room
temperature. After that, about 10 mL of diluted hydrochloric acid (1.0
mol/L) was added to this solution, followed by stirring for 1 hour. Then,
the aqueous layer of this mixture was extracted with ethyl acetate, and
the ethyl acetate solution and the organic layer were combined and washed
with saturated brine. The organic layer was dried with magnesium sulfate.
Then, this mixture was gravity filtered. The resulting filtrate was
concentrated to give a solid, and a mixed solvent of chloroform and
hexane was added to the solid. The mixture was irradiated with ultrasonic
waves, whereby a solid was precipitated. This solid was collected by
suction filtration to give 0.62 g of a light-brown powder in
58%quadrature yield, which was the substance to be produced.

[0326] In a 50 mL three-neck flask were put 0.62 g (1.3 mmol) of
2-iode-9,10-diphenylanthracene, 0.60 g (1.3 mmol) of
3-(2,8-diphenyldibenzofuran-4-yl)phenylboronic acid, and 99 mg (0.33
mmol) of tri(ortho-tolyl)phosphine. The air in the flask was replaced
with nitrogen. To this mixture were added 10 mL of toluene, 3.0 mL of
ethanol, and 2.0 mL of an aqueous solution of potassium carbonate (2.0
mol/L). While the pressure was reduced, this mixture was stirred to be
degassed. To this mixture was added 15 mg (0.065 mmol) of palladium(II)
acetate, and the mixture was stirred at 80° C. for 4 hours. Then,
the aqueous layer of the obtained mixture was extracted with toluene, and
the toluene solution and the organic layer were combined and washed with
saturated brine. The organic layer was dried with magnesium sulfate.
Then, this mixture was gravity filtered. The resulting filtrate was
concentrated to given an oily substance, and the obtained oily substance
was purified by silica gel column chromatography to give a yellow oily
substance. The chromatography was carried out using a mixed solvent
having a 3:1 ratio of hexane to toluene as a developing solvent.
Recrystallization of the oily substance from a mixed solvent of toluene
and hexane gave 0.55 g of a yellow powder in 58% yield, which was the
substance to be produced.

[0327] By a train sublimation method, 0.55 g of the obtained yellow
powdered solid was purified. In the purification, the yellow powdered
solid was heated at 320° C. under a pressure of 3.0 Pa with a flow
rate of argon gas of 4.0 mL/min. After the purification, 0.50 g of a
yellow solid was obtained in a yield of 90%, which was the substance to
be produced.

[0328] A nuclear magnetic resonance (NMR) method identified this compound
as 4-[3-(9,10-diphenyl-2-anthryl)phenyl]-2,8-diphenyldibenzofuran
(abbreviation: 2mDBFPPA-III), which was the substance to be produced.

[0330] FIGS. 38A and 38B show the 1H NMR charts. Note that FIG. 38B
is a chart showing an enlarged part of FIG. 38A in the range of 7.2 to
8.3 ppm.

[0331] Thermogravimetry-differential thermal analysis (TG-DTA) of
2mDBFPPA-III, which was obtained, was performed. A high vacuum
differential type differential thermal balance (manufactured by Bruker
AXS K.K., TG/DTA 2410SA) was used for the measurement. The measurement
was carried out under a nitrogen stream (a flow rate of 200 mL/min) and a
normal pressure at a temperature rising rate of 10° C./min. The
relationship between weight and temperature (thermogravimetry)
demonstrates that the temperature at which the weight at the start of the
measurement is reduced by 5% (5% weight loss temperature) is 448°
C., which is indicative of high heat resistance.

[0332] Further, FIG. 39A shows an absorption spectrum of a toluene
solution of 2mDBFPPA-III, and FIG. 39B shows an emission spectrum
thereof. FIG. 40A shows an absorption spectrum of a thin film of
2mDBFPPA-III, and FIG. 40B shows an emission spectrum thereof. The
absorption spectrum was measured using an ultraviolet-visible
spectrophotometer (V-550, produced by JASCO Corporation). The
measurements were performed with samples prepared in such a manner that
the solution was put in a quartz cell while the thin film was obtained by
evaporation onto a quartz substrate. The absorption spectrum of the
solution was obtained by subtracting the absorption spectra of quartz and
toluene from those of quartz and the solution, and the absorption
spectrum of the thin film was obtained by subtracting the absorption
spectrum of a quartz substrate from those of the quartz substrate and the
thin film. In FIGS. 39A and 39B and FIGS. 40A and 40B, the horizontal
axis represents wavelength (nm) and the vertical axis represents
intensity (arbitrary unit). In the case of the toluene solution,
absorption was observed at around 365 nm, 385 nm and 406 nm and the
emission wavelengths were 423 nm and 447 nm (excitation wavelength: 385
nm). In the case of the thin film, absorption was observed at around 288
nm, 371 nm, 391 nm and 414 nm, and the emission wavelengths were 439 nm
and 459 nm (excitation wavelength: 413 nm).

[0333] The HOMO level and the LUMO level of the thin film of 2mDBFPPA-III
were measured. The value of the HOMO level was obtained by conversion of
a value of the ionization potential measured with a photoelectron
spectrometer (AC-2, manufactured by Riken Keiki Co., Ltd.) in the
atmosphere into a negative value. The value of the LUMO level was
obtained in such a manner that the absorption edge, which was obtained
from Tauc plot with an assumption of direct transition using data on the
absorption spectrum of the thin film of 2mDBFPPA-III which is shown in
FIG. 40A, was regarded as an optical energy gap and added to the value of
the HOMO level. As a result, the HOMO level and LUMO level of
2mDBFPPA-III were found to be -5.77 eV and -2.92 eV, respectively.

[0334] The oxidation characteristic and reduction characteristic of
2mDBFPPA-III were measured. In the measurements of the oxidation and
reduction characteristics, cyclic voltammetry (CV) measurement was
employed, and an electrochemical analyzer (ALS model 600A, manufactured
by BAS Inc.) was used.

[0335] As a solution used in the CV measurement, dehydrated
N,N-dimethylformamide (DMF, product of Sigma-Aldrich Inc., 99.8%, catalog
No. 22705-6) was used as a solvent, and tetra-n-butylammonium perchlorate
(n-Bu4NClO4, product of Tokyo Chemical Industry Co., Ltd.,
catalog No. T0836), which was a supporting electrolyte, was dissolved in
the solvent such that the concentration of tetra-n-butylammonium
perchlorate was 100 mmol/L. Further, the object to be measured was
dissolved in the solvent such that the concentration thereof was 1
mmol/L. A platinum electrode (manufactured by BAS Inc., PTE platinum
electrode) was used as a working electrode, a platinum electrode
(manufactured by BAS Inc., Pt counter electrode for VC-3, (5 cm)) was
used as an auxiliary electrode, and an Ag/Ag.sup.+ electrode
(manufactured by BAS Inc., RE-5 reference electrode for nonaqueous
solvent) was used as a reference electrode. Note that the measurement was
conducted at room temperature. In addition, the scan rate at the CV
measurement was set to 0.1 V/s in all the measurement.

[0336] The reduction characteristic of 2mDBFPPA-III was examined by 100
measurement cycles in which the potential of the working electrode with
respect to the reference electrode was scanned from -1.59 V to -2.25 V
and then from -2.25 V to -1.59 V in each cycle. Similarly, the oxidation
characteristic of 2mDBFPPA-III was evaluated by 100 measurement cycles in
which the potential of the working electrode with respect to the
reference electrode was scanned from 0.25 V to 1.00 V and then from 1.00
V to 0.25 V in each cycle.

[0337] According to the measurement results, a peak current corresponding
to oxidation at around 0.88 V (vs. Ag/Ag.sup.+) and a peak current
corresponding to reduction at around -2.16 V (vs. Ag/Ag.sup.+) were
observed. FIG. 41 shows a graph of the results.

[0338] Even after as many as 100 scan cycles, 2mDBFPPA-III showed no
significant change in the peak position of the CV curves representing
oxidation and reduction and kept the peak intensity at 81% of the initial
intensity on the oxidation side and at 87% on the reduction side. Thus,
it is understood that 2mDBFPPA-III is relatively stable, when subjected
to repetitions of oxidation from a neutral state to an oxidized state and
reduction from the oxidized state to the neutral state or repetitions of
reduction from a neutral state to a reduced state and oxidation from the
reduced state to the neutral state.

Example 8

[0339] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37A. Chemical
formulae of materials used in this example are shown below.

##STR00087##

[0340] A method of fabricating Light-emitting Element 5 of this example
will now be described.

(Light-Emitting Element 5)

[0341] First, ITSO was deposited over the glass substrate 1100 by a
sputtering method, whereby the first electrode 1101 was formed. Its
thickness was 110 nm and the electrode area was 2 mm×2 mm. Here,
the first electrode 1101 is an electrode that functions as an anode of
the light-emitting element.

[0342] Next, as pretreatment for forming the light-emitting element over
the substrate 1100, a surface of the substrate was washed with water,
baked at 200° C. for one hour, and subjected to UV ozone treatment
for 370 seconds.

[0343] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10-4 Pa, and subjected to vacuum baking at 170°
C. for 30 minutes in a heating chamber of the vacuum evaporation
apparatus, and then the substrate 1100 was cooled down for about 30
minutes.

[0344] Next, the substrate 1100 was fixed to a substrate holder in a
vacuum evaporation apparatus so that a surface of the substrate 1100 on
which the first electrode 1101 was formed faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10-4 Pa. Then,
by an evaporation method using resistance heating,
9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:
PCzPA) which is a substance having a high hole-transport property and
molybdenum(VI) oxide which is an acceptor substance were co-evaporated to
form the hole-injection layer 1111 over the first electrode 1101. The
thickness of the hole-injection layer 1111 was 50 nm, and the weight
ratio of PCzPA to molybdenum(VI) oxide was controlled to be 4:2
(=PCzPA:molybdenum(VI) oxide). Note that the co-evaporation method refers
to an evaporation method in which evaporation is carried out from a
plurality of evaporation sources at the same time in one treatment
chamber.

[0345] Next, PCzPA was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby the hole-transport layer 1112 was
formed.

[0346] Furthermore,
4-[3-(9,10-diphenyl-2-anthryl)phenyl]-2,8-diphenyldibenzofuran
(abbreviation: 2mDBFPPA-III) synthesized in Example 7 and
N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenyl-pyrene-1,6-dia-
mine (abbreviation: 1,6FLPAPrn) were co-evaporated to form the
light-emitting layer 1113 over the hole-transport layer. The weight ratio
of 2mDBFPPA-III to 1,6FLPAPrn was adjusted to 1:0.05
(=2mDBFPPA-III:1,6FLPAPrn). The thickness of the light-emitting layer
1113 was set to 30 nm.

[0347] Then, over the light-emitting layer 1113, a 10 nm thick layer of
Alq and, a 15 nm thick layer of BPhen were deposited on the Alq layer,
whereby the electron-transport layer 1114 including Alq and BPhen was
obtained.

[0348] Further, a 1 nm thick film of LiF was formed over the
electron-transport layer 1114 by evaporation, whereby the
electron-injection layer 1115 was formed.

[0349] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 5 of this example was fabricated.

[0350] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

[0352] Light-emitting Element 5 was sealed in a glove box containing a
nitrogen atmosphere so as not to be exposed to air. Then, operation
characteristics of the Light-emitting Element 5 were measured. Note that
the measurement was carried out at room temperature (in the atmosphere
kept at 25° C.).

[0354] As seen from FIG. 45 and the CIE chromaticity coordinates in Table
10, blue light emission is shown by Light-emitting Element 5, which was
formed. FIG. 42, FIG. 43, FIG. 44, and Table 10 reveal that
Light-emitting Element 5 exhibits good chromaticity, high current
efficiency, and high external quantum efficiency.

[0355] As described above, 2mDBFPPA-III produced in Example 7 was used as
the host material of the light-emitting layer, whereby the light-emitting
element achieved good chromaticity and high emission efficiency.

[0356] Next, Light-emitting Element 5 was subjected to reliability tests.
Results of the reliability tests are shown in FIG. 46. In FIG. 46, the
vertical axis represents normalized luminance (%) with an initial
luminance of 100%, and the horizontal axis represents driving time (h) of
the element. In the reliability tests, Light-emitting Element 5 of this
example was driven under the conditions where the current density was
constant and the initial luminance was 1000 cd/m2. FIG. 46 shows
that Light-emitting Element 5 kept 81% of the initial luminance after the
driving for 1300 hours. Thus, Light-emitting Element 5 shows high
reliability. Furthermore, the results of the reliability tests
demonstrate that the light-emitting element to which one embodiment of
the present invention is applied is effective in realizing a
light-emitting element having a long lifetime.

Example 9

Synthesis Example 4

[0357] This example will show a method of synthesizing
2-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA)) represented by Structural formula (158) described in
Embodiment 1.

##STR00088##

Step 1: Synthesis of dibenzofuran-2-boronic acid

[0358] The synthesis scheme of Step 1 is shown in (F-1).

##STR00089##

[0359] In a 300 mL three-neck flask was put 3.6 g (14 mmol) of
3-bromodibenzofuran. The air in the flask was replaced with nitrogen. To
this mixture was added 70 mL of THF, and this solution was cooled to
-80° C. Then, 10 mL (16 mmol) of n-butyllithium (a 1.6 mol/L
hexane solution) was dripped into this solution with a syringe. After
that, this solution was stirred at the same temperature for 2 hours.
Then, 3.4 mL (30 mmol) of trimethyl borate was added to this solution,
and the mixture was stirred for 4 days while its temperature was returned
to room temperature. After that, about 30 mL of diluted hydrochloric acid
(1.0 mol/L) was added to this solution, followed by stirring for 1 hour.
Then, the aqueous layer of this mixture was extracted with ethyl acetate,
and the ethyl acetate solution and the organic layer were combined and
washed with saturated brine. The organic layer was dried with magnesium
sulfate. Then, this mixture was gravity filtered. The resulting filtrate
was concentrated to give a solid. The solid was washed with hexane,
whereby 0.70 g of a white powder was obtained in 27% yield, which was the
substance to be produced.

[0361] In a 50 mL three-neck flask were put 1.2 g (2.4 mmol) of
2-(3-bromophenyl)-9,10-diphenylanthracene, 0.52 g (2.4 mmol) of
dibenzofuran-2-boronic acid, and 0.18 g (0.60 mmol) of
tri(ortho-tolyl)phosphine. The air in the flask was replaced with
nitrogen. To this mixture were added 10 mL of toluene, 3.0 mL of ethanol,
and 3.0 mL of an aqueous solution of sodium carbonate (2.0 mol/L). While
the pressure was reduced, this mixture was stirred to be degassed. To
this mixture was added 27 mg (0.12 mmol) of palladium(II) acetate, and
the mixture was stirred at 80° C. for 3 hours. Then, the aqueous
layer of the obtained mixture was extracted with toluene, and the toluene
solution and the organic layer were combined and washed with saturated
brine. The organic layer was dried with magnesium sulfate. Then, this
mixture was gravity filtered. The resulting filtrate was concentrated,
and the obtained oily substance was purified by silica gel column
chromatography to give a yellow oily substance. The chromatography was
carried out using a mixed solvent having a 5:1 ratio of hexane to toluene
as a developing solvent, whereby an oily substance was obtained.
Recrystallization of the oily substance from a mixed solvent of toluene
and hexane gave 0.40 g of a yellow powder in 29% yield, which was the
substance to be produced.

[0362] By a train sublimation method, 0.40 g of the obtained yellow
powdered solid was purified. In the purification, the yellow powdered
solid was heated at 270° C. under a pressure of 2.6 Pa with a flow
rate of argon gas of 5.0 mL/min. After the purification, 0.35 g of a
yellow solid was obtained in a yield of 87%, which was the substance to
be produced.

[0363] A nuclear magnetic resonance (NMR) method identified this compound
as 2-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA), which was the substance to be produced.

[0365] FIGS. 47A and 47B show the 1H NMR charts. Note that FIG. 47B
is a chart showing an enlarged part of FIG. 47A in the range of 7.2 to
8.2 ppm.

[0366] Thermogravimetry-differential thermal analysis (TG-DTA) of
2mDBFPPA, which was obtained, was performed. A high vacuum differential
type differential thermal balance (manufactured by Bruker AXS K.K.,
TG/DTA 2410SA) was used for the measurement. The measurement was carried
out under a nitrogen stream (a flow rate of 200 mL/min) and a normal
pressure at a temperature rising rate of 10° C./min. The
relationship between weight and temperature (thermogravimetry)
demonstrates that the temperature at which the weight at the start of the
measurement is reduced by 5% (5% weight loss temperature) is 415°
C., which is indicative of high heat resistance.

[0367] Further, FIG. 48A shows an absorption spectrum of a toluene
solution of 2mDBFPPA, and FIG. 48B shows an emission spectrum thereof.
FIG. 49A shows an absorption spectrum of a thin film of 2mDBFPPA, and
FIG. 49B shows an emission spectrum thereof. The absorption spectrum was
measured using an ultraviolet-visible spectrophotometer (V-550, produced
by JASCO Corporation). The measurements were performed with samples
prepared in such a manner that the solution was put in a quartz cell
while the thin film was obtained by evaporation onto a quartz substrate.
The absorption spectrum of the solution was obtained by subtracting the
absorption spectra of quartz and toluene from those of quartz and the
solution, and the absorption spectrum of the thin film was obtained by
subtracting the absorption spectrum of a quartz substrate from those of
the quartz substrate and the thin film. In FIGS. 48A and 48B and FIGS.
49A and 49B, the horizontal axis represents wavelength (nm) and the
vertical axis represents intensity (arbitrary unit). In the case of the
toluene solution, absorption was observed at around 291 nm, 366 nm, 384
nm, and 406 nm and the emission wavelengths were 423 nm and 446 nm
(excitation wavelength: 385 nm). In the case of the thin film, absorption
was observed at around 246 nm, 293 nm, 371 nm and 413 nm, and the
emission wavelengths were 437 nm and 459 nm (excitation wavelength: 413
nm).

[0368] The HOMO level and the LUMO level of the thin film of 2mDBFPPA were
measured. The value of the HOMO level was obtained by conversion of a
value of the ionization potential measured with a photoelectron
spectrometer (AC-2, manufactured by Riken Keiki Co., Ltd.) in the
atmosphere into a negative value. The value of the LUMO level was
obtained in such a manner that the absorption edge, which was obtained
from Tauc plot with an assumption of direct transition using data on the
absorption spectrum of the thin film of 2mDBFPPA which is shown in FIG.
49A, was regarded as an optical energy gap and added to the value of the
HOMO level. As a result, the HOMO level and LUMO level of 2mDBFPPA were
found to be -5.71 eV and -2.85 eV, respectively.

[0369] The oxidation characteristic and reduction characteristic of
2mDBFPPA were measured. In the measurements of the oxidation and
reduction characteristics, cyclic voltammetry (CV) measurement was
employed, and an electrochemical analyzer (ALS model 600A, manufactured
by BAS Inc.) was used.

[0370] As a solution used in the CV measurement, dehydrated
N,N-dimethylformamide (DMF, product of Sigma-Aldrich Inc., 99.8%, catalog
No. 22705-6) was used as a solvent, and tetra-n-butylammonium perchlorate
(n-Bu4NClO4, product of Tokyo Chemical Industry Co., Ltd.,
catalog No. T0836), which was a supporting electrolyte, was dissolved in
the solvent such that the concentration of tetra-n-butylammonium
perchlorate was 100 mmol/L. Further, the object to be measured was
dissolved in the solvent such that the concentration thereof was 1
mmol/L. A platinum electrode (manufactured by BAS Inc., PTE platinum
electrode) was used as a working electrode, a platinum electrode
(manufactured by BAS Inc., Pt counter electrode for VC-3, (5 cm)) was
used as an auxiliary electrode, and an Ag/Ag.sup.+ electrode
(manufactured by BAS Inc., RE-5 reference electrode for nonaqueous
solvent) was used as a reference electrode. Note that the measurement was
conducted at room temperature. In addition, the scan rate at the CV
measurement was set to 0.1 V/s in all the measurement.

[0371] The reduction characteristic of 2mDBFPPA was examined by 100
measurement cycles in which the potential of the working electrode with
respect to the reference electrode was scanned from -1.56 V to -2.27 V
and then from -2.27 V to -1.56 V in each cycle. Similarly, the oxidation
characteristic of 2mDBFPPA was evaluated by 100 measurement cycles in
which the potential of the working electrode with respect to the
reference electrode was scanned from 0.20 V to 1.05 V and then from 1.05
V to 0.20 V in each cycle.

[0372] According to the measurement results, a peak current corresponding
to oxidation at around 0.95 V (vs. Ag/Ag.sup.+) and a peak current
corresponding to reduction at around -2.22 V (vs. Ag/Ag.sup.+) were
observed. FIG. 50 shows a graph of the results.

[0373] Even after as many as 100 scan cycles, 2mDBFPPA showed no
significant change in the peak position of the CV curves representing
oxidation and reduction and kept the peak intensity at 73% of the initial
intensity on the oxidation side and at 89% on the reduction side. Thus,
it is understood that 2mDBFPPA is relatively stable, when subjected to
repetitions of oxidation from a neutral state to an oxidized state and
reduction from the oxidized state to the neutral state or repetitions of
reduction from a neutral state to a reduced state and oxidation from the
reduced state to the neutral state.

Example 10

[0374] In this example, a light-emitting element of one embodiment of the
present invention will be described referring to FIG. 37A. Chemical
formulae of materials used in this example are shown below.

##STR00091##

[0375] A method of fabricating Light-emitting Element 6 of this example
will now be described.

(Light-Emitting Element 6)

[0376] First, ITSO was deposited over the glass substrate 1100 by a
sputtering method, whereby the first electrode 1101 was formed. Its
thickness was 110 nm and the electrode area was 2 mm×2 mm. Here,
the first electrode 1101 is an electrode that functions as an anode of
the light-emitting element.

[0377] Next, as pretreatment for forming the light-emitting element over
the substrate 1100, a surface of the substrate was washed with water,
baked at 200° C. for one hour, and subjected to UV ozone treatment
for 370 seconds.

[0378] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10-4 Pa, and subjected to vacuum baking at 170°
C. for 30 minutes in a heating chamber of the vacuum evaporation
apparatus, and then the substrate 1100 was cooled down for about 30
minutes.

[0379] Next, the substrate 1100 was fixed to a substrate holder in a
vacuum evaporation apparatus so that a surface of the substrate 1100 on
which the first electrode 1101 was formed faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10-4 Pa. Then,
by an evaporation method using resistance heating, PCzPA which is a
substance having a high hole-transport property and molybdenum(VI) oxide
which is an acceptor substance were co-evaporated to form the
hole-injection layer 1111 over the first electrode 1101. The thickness of
the hole-injection layer 1111 was 50 nm, and the weight ratio of PCzPA to
molybdenum(VI) oxide was controlled to be 4:2 (=PCzPA:molybdenum(VI)
oxide). Note that the co-evaporation method refers to an evaporation
method in which evaporation is carried out from a plurality of
evaporation sources at the same time in one treatment chamber.

[0380] Next, PCzPA was deposited to a thickness of 10 nm over the
hole-injection layer 1111, whereby the hole-transport layer 1112 was
formed.

[0381] Furthermore, 2-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran
(abbreviation: 2mDBFPPA) synthesized in Example 9 and 1,6FLPAPrn were
co-evaporated to form the light-emitting layer 1113 over the
hole-transport layer. The weight ratio of 2mDBFPPA to 1,6FLPAPrn was
adjusted to 1:0.05 (=2mDBFPPA:1,6FLPAPrn). The thickness of the
light-emitting layer 1113 was set to 30 nm.

[0382] Then, over the light-emitting layer 1113, a 10 nm thick layer of
Alq and, a 15 nm thick layer of BPhen were deposited on the Alq layer,
whereby the electron-transport layer 1114 including Alq and BPhen was
obtained.

[0383] Further, a 1 nm thick film of LiF was formed over the
electron-transport layer 1114 by evaporation, whereby the
electron-injection layer 1115 was formed.

[0384] Lastly, a 200 nm thick film of aluminum was formed by evaporation
to form a second electrode 1103 functioning as a cathode. Thus,
Light-emitting Element 6 of this example was fabricated.

[0385] Note that, in the above evaporation process, evaporation was all
performed by a resistance heating method.

[0387] Light-emitting Element 6 was sealed in a glove box containing a
nitrogen atmosphere so as not to be exposed to air. Then, operation
characteristics of the Light-emitting Element 6 were measured. Note that
the measurement was carried out at room temperature (in the atmosphere
kept at 25° C.).

[0389] As seen from FIG. 54 and the CIE chromaticity coordinates in Table
12, blue light emission is shown by Light-emitting Element 6, which was
formed. FIG. 51, FIG. 52, FIG. 53, and Table 12 reveal that
Light-emitting Element 6 exhibits good chromaticity, high current
efficiency, and high external quantum efficiency.

[0390] As described above, 2mDBFPPA produced in Example 9 was used as the
host material of the light-emitting layer, whereby the light-emitting
element achieved good chromaticity and high emission efficiency.

Reference Example 1

[0391] A method for synthesizing
4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation:
BPAFLBi) used in Examples 3 and 4 above will be specifically described.
The structure of BPAFLBi is shown below.

##STR00092##

Step 1: Synthesis Method of 9-(4'-bromo-4-biphenyl)-9-phenylfluorene

[0392] In a 500-mL three-neck flask was put 5.1 g (22 mmol) of
2-bromobiphenyl. The air in the flask was replaced with nitrogen. Then,
200 mL of tetrahydrofuran (abbreviation: THF) was added to the mixture,
and the mixture was cooled to -78° C. Then, 14 mL (22 mmol) of an
n-butyllithium hexane solution was dripped into this mixture solution,
and the mixture was stirred for 2.5 hours. After that, 6.7 g (20 mmol) of
9-(4'-bromobiphenylyl)-9-phenylfluoren was added to this mixture, and the
mixture was stirred at -78° C. for 2 hours and then at room
temperature for 85 hours.

[0393] After reaction, 1N-diluted hydrochloric acid was added to this
reaction solution until the mixed solution was made acid, and the mixture
was stirred for 4 hours. The mixture was washed with water. After that,
magnesium sulfate was added to the mixture so that moisture is removed.
This suspension was filtered, and the filtrate was concentrated. The
resulting substance was purified by silica gel column chromatography (the
developing solvent was hexane). The obtained fractions were concentrated,
followed by addition of methanol thereto. The resulting substance was
irradiated with ultrasonic waves, and then recrystallized to give a white
powder, which was the substance to be produced.

[0394] In a 200-mL recovery flask were put this white powder, 50 mL of
glacial acetic acid, and 1.0 mL of hydrochloric acid. The mixture was
heated, and stirred under a nitrogen atmosphere at 130° C. for 2.5
hours to be reacted.

[0395] After reaction, this reaction mixture solution was filtered. The
resulting filtrate was dissolved in 100 mL of toluene, and the mixture
was washed with water, aqueous sodium hydroxide, and water in this order.
Magnesium sulfate was added to the mixture so that moisture is removed.
This suspension was filtered, and the resulting filtrate was
concentrated. Acetone and methanol were added to the resulting substance.
The mixture was irradiated with ultrasonic waves and then recrystallized
to give 6.3 g of a white powder in a yield of 67%, which was the
substance to be produced. The reaction scheme is shown in the following
(J-1).

[0396] In a 100 mL three-neck flask were put 3.8 g (8.0 mmol) of
9-(4'-bromo-4-biphenyl)-9-phenylfluorene, 2.0 g (8.0 mmol) of
4-phenyl-diphenylamine, 1.0 g (10 mmol) of sodium tert-butoxide, and 23
mg (0.04 mmol) of bis(dibenzylideneacetone)palladium(0). The air in the
flask was replaced with nitrogen. Then, 20 mL of dehydrated xylene was
added to this mixture. After the mixture was degassed while being stirred
under reduced pressure, 0.2 mL (0.1 mmol) of tri(tert-butyl)phosphine (10
wt % hexane solution) was added to the mixture. This mixture was heated
and stirred under a nitrogen atmosphere at 110° C. for 2 hours to
be reacted.

[0397] After reaction, 200 mL of toluene was added to the reaction mixture
solution, and the resulting suspension was filtered through Florisil
(produced by Wako Pure Chemical Industries, Ltd., Catalog No. 540-00135)
and Celite (produced by Wako Pure Chemical Industries, Ltd., Catalog No.
531-16855). The resulting filtrate was concentrated. The resulting
substance was purified by silica gel column chromatography (the
developing solvent has a 1:4 ratio of toluene to hexane). The obtained
fractions were concentrated, and acetone and methanol were added to the
mixture. The mixture was irradiated with ultrasonic waves and then
recrystallized to give 4.4 g of a white powder in a yield of 86%, which
was the substance to be produced. The reaction scheme of the above
synthesis method is shown in the following (J-2).

##STR00094##

[0398] The Rf values of the produced substance,
9-(4'-bromo-4-biphenyl)-9-phenylfluorene, and 4-phenyl-diphenylamine were
respectively 0.51, 0.56, and 0.28, which were found by silica gel thin
layer chromatography (TLC) (the developing solvent has a 1:10 ratio of
ethyl acetate to hexane).

[0399] The compound obtained through the above Step 2 was subjected to a
nuclear magnetic resonance (NMR) method. The measurement data are shown
below. The measurement results indicate that the obtained compound was
BPAFLBi, which is a fluorene derivative.

[0401] A method for synthesizing
4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP)
used in Examples 5 and 6 above will be specifically described. The
structure of BPAFLP is shown below.

##STR00095##

Step 1: Synthesis method of 9-(4-bromophenyl)-9-phenylfluorene

[0402] In a 100-mL three-neck flask, 1.2 g (50 mmol) of magnesium was
heated and stirred under reduced pressure for 30 minutes to be activated.
After the flask was cooled to room temperature and was made to have a
nitrogen atmosphere, several drops of dibromoethane were added, so that
foam formation and heat generation were confirmed. After 12 g (50 mmol)
of 2-bromobiphenyl dissolved in 10 mL of diethyl ether was slowly dripped
into this mixture, the mixture was stirred and heated under reflux for
2.5 hours. Accordingly, a Grignard reagent was prepared.

[0403] In a 500-mL three-neck flask were put 10 g (40 mmol) of
4-bromobenzophenone and 100 mL of diethyl ether. After the Grignard
reagent prepared as above was slowly dripped into this mixture, the
mixture was heated and stirred under reflux for 9 hours.

[0404] After reaction, this mixture was filtered to give a residue. The
residue was dissolved in 150 mL of ethyl acetate, and 1N-hydrochloric
acid was added to the mixture, which was then stirred for 2 hours until
it was made acid. The organic layer of the liquid was washed with water.
Then, magnesium sulfate was added thereto so that moisture is removed.
This suspension was filtered, and the resulting filtrate was concentrated
to give a candy-like substance.

[0405] In a 500-mL recovery flask were put this candy-like substance, 50
mL of glacial acetic acid, and 1.0 mL of hydrochloric acid. The mixture
was heated and stirred under a nitrogen atmosphere at 130° C. for
1.5 hours to be reacted.

[0406] After reaction, this reaction mixture solution was filtered to give
a residue. The residue was washed with water, aqueous sodium hydroxide,
water, and methanol in this order. Then, the mixture was dried to give 11
g of a white powder in 69% yield, Which was the substance to be produced.
The reaction scheme of the synthesis method is shown in the following
(J-3).

[0407] In a 100-mL three-neck flask were put 3.2 g (8.0 mmol) of
9-(4-bromophenyl)-9-phenylfluorene, 2.0 g (8.0 mmol) of
4-phenyl-diphenylamine, 1.0 g (10 mmol) of sodium tert-butoxide and 23 mg
(0.04 mmol) of bis(dibenzylideneacetone)palladium(0). The air in the
flask was replaced with nitrogen. Then, 20 mL of dehydrated xylene was
added to this mixture. After the mixture was degassed while being stirred
under reduced pressure, 0.2 mL (0.1 mmol) of tri(tert-butyl)phosphine (a
10 wt % hexane solution) was added to the mixture. This mixture was
heated and stirred under a nitrogen atmosphere at 110° C. for 2
hours to be reacted.

[0408] After reaction, 200 mL of toluene was added to the reaction mixture
solution, and the resulting suspension was filtered through Florisil
(produced by Wako Pure Chemical Industries, Ltd., Catalog No. 540-00135)
and Celite (produced by Wako Pure Chemical Industries, Ltd., Catalog No.
531-16855). The filtrate was concentrated, and the resulting substance
was purified by silica gel column chromatography (the developing solvent
has a 1:4 ratio of toluene to hexane). The obtained fractions were
concentrated, and acetone and methanol were added to the mixture. The
mixture was irradiated with ultrasonic waves and then recrystallized to
give 4.1 g of a white powder in 92% yield, which was the substance to be
produced. The reaction scheme of the above synthesis method is shown in
the following (J-4).

##STR00097##

[0409] The Rf values of the produced substance,
9-(4-bromophenyl)-9-phenylfluorene, and 4-phenyl-diphenylamine were
respectively 0.41, 0.51, and 0.27, which were found by silica gel thin
layer chromatography (TLC) (the developing solvent has a 1:10 ratio of
ethyl acetate to hexane).

[0410] The compound obtained through the above Step 2 was subjected to a
nuclear magnetic resonance (NMR) method. The measurement data are shown
below. The measurement results indicate that the obtained compound was
BPAFLP, which is a fluorene derivative.

[0413] In a 200 mL three-neck flask were put 5.8 g (14.6 mmol) of
9-(4-bromophenyl)-9-phenylfluorene, 1.7 mL (18.6 mmol) of aniline, and
4.2 g (44.0 mmol) of sodium tert-butoxide. The air in the flask was
replaced with nitrogen. To this mixture were added 147.0 mL of toluene
and 0.4 mL of a 10 wt % hexane solution of tri(tert-butyl)phosphine. The
temperature of this mixture was set to 60° C., and 66.1 mg (0.1
mmol) of bis(dibenzylideneacetone)palladium(0) was added to the mixture,
followed by stirring for 3.5 hours. After the stirring, the mixture was
suction-filtered through Florisil (produced by Wako Pure Chemical
Industries, Ltd., Catalog No. 540-00135), Celite (produced by Wako Pure
Chemical Industries, Ltd., Catalog No. 531-16855), and alumina. The
resulting filtrate was concentrated to give a solid, which was then
purified by silica gel column chromatography (the developing solvent has
a 2:1 ratio of hexane to toluene). The obtained fractions were
concentrated to give 6.0 g of a while solid in 99% yield, which was the
substance to be produced. The synthesis scheme of Step 1 is shown in
(E1-2) below.

[0414] In a 50 mL three-neck flask were put 0.4 g (1.2 mmol) of
1,6-dibromopyrene, 1.0 g (2.4 mmol) of
4-(9-phenyl-9H-fluoren-9-yl)diphenylamine (abbreviation: FLPA) and 0.3 g
(3.6 mmol) of sodium tert-butoxide. The air in the flask was replaced
with nitrogen. To this mixture were added 11.5 mL of toluene and 0.2 mL
of a 10 wt % hexane solution of tri(tert-butyl)phosphine. The temperature
of this mixture was set to 70° C., and 31.1 mg (0.05 mmol) of
bis(dibenzylideneacetone)palladium(0) was added to the mixture, followed
by stirring for 4.0 hours. After the stirring, the mixture was
suction-filtered through Florisil, Celite, and alumina. The resulting
filtrate was concentrated to give a solid, which was then purified by
silica gel column chromatography (the developing solvent was chloroform).
The obtained fractions were concentrated to give a yellow solid. The
obtained solid was washed with a mixed solvent of toluene and hexane, and
then the mixture was suction-filtered to give a yellow solid. The
obtained yellow solid was washed with a mixed solvent of chloroform and
hexane, whereby 0.8 g of a pale yellow powdered solid was obtained in 68%
yield, which was the substance to be produced.

[0415] By a train sublimation method, 0.8 g of the obtained yellow solid
was purified. Under a pressure of 2.7 Pa with a flow rate of argon at 5
mL/min, the sublimation purification was carried out at 360° C.
After the purification, 0.4 g of the substance to be produced was
obtained in a yield of 56%. The synthesis scheme of the above step is
shown in the following (E2).

##STR00100##

[0416] A nuclear magnetic resonance (NMR) method and a mass spectrometry
identified this compound as
N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N-diphenyl-pyrene-1,6-diam-
ine (abbreviation: 1,6FLPAPrn), which was the substance to be produced.

[0418] This application is based on Japanese Patent Application serial no.
2009-260240 filed with the Japan Patent Office on Nov. 13, 2009, the
entire contents of which are hereby incorporated by reference.